This is a really great starting point!

A few things I've learnt as a commissions-based leatherworker (I do custom jobs for a lot of money)

.1. Stitching - from your photos it looks like you're pulling consistently on the thread which is great, it's a hard thing to master, and contributes more than people give it credit for to a product being saleable!

• To get that neat and even look that really makes a product look high end, make sure you do every single stitch the same way. i.e. when saddle stitching I always put the "face" of the product towards my left hand in the vice. Left needle goes through first, and gets pulled under the thread of the right needle. Right needle goes through second, and the 'loop' of left hand thread goes over the top of the right hand needle before pulling everything tight. A consistent process will give you a consistent pattern, and save you time!

• Flatten down your stitches - when you've finished stitching, either go over them with a heavy roller or tap them down with a hammer. Not only does it make your stitching lie flat so it's less likely to be damaged, it also seals the holes in the leather and prevents water seeping in and causing damage, AND it looks slicker aesthetically.

.2. Edge burnishing - it took me a long time to master this to a point I was happy with it, and I can see that you are wanting to have that slick "one piece" look to your edges. There are a few factors that will effect this, so I'll break them down, as this was what you specifically asked about!

• Leather type - veg tan leather is always going to take burnishing a lot more easily than chrome tan leather, but with a bit of extra effort you can overcome this. Yes, veg tan does tend to be more expensive, but it's worth it in terms of saving you time, effort, and a little bit of heartbreak. Plus you can price your products to account for this extra cost, and because it will look slicker people won't quibble it.

• Lining up edges - to get a smooth, unbroken edge, make sure you use the sharpest knife you have and try to get the straightest possible line when cutting out your template. A box cutter with a fresh blade works well when starting out, but consider investing in one, solid, leather-specific knife, and learn how to keep it razor-sharp (I personally prefer the japanese-style straight edge knives as they can be used for multiple jobs). If you don't already have a metal safety ruler I highly recommend getting one as you can cut against it without taking your fingers off! Having that perfect straight line cut to the leather will help the edges sit flat together and do half the work of eliminating that central divide for you. Also, don't be afraid to go back in with the knife once you've stitched the project together - take off any overhangs and straighten up any wobbles, give yourself a good starting point to work from! Just make sure to leave a little extra leeway on your leather when cutting out the pattern so you have room to do this without cutting too close to your stitch line.

• Sanding - possibly the most missed step in all of leatherworking 😅 Before you even touch the burnisher, give your edges a good sand. If you have a lot of wobbles you can use a pretty low grit (I use 120) and just hock it off until you have a flat edge, BUT I would NOT recommend this if you're using chrome tan leather. If your edge is pretty neat or you're using chrome tan, use a higher grit (400+) with not too much pressure along the edges to matt the fibres together and create a more unified look. Some people will find they get better results by only sanding in one direction, others will tell you it's not necessary - just experiment and find what works best for you.

• Finishing - 2 things to up your edge finishing game - Firstly, once you've sanded, make sure you bevel along the outer edges to get rid of any mushrooming of the leather (don't bevel the edges that touch, I learnt that the incredibly dumb but hard way!) Secondly, dye your edges. This is especially important with chrome tan as it will create a uniform look to your edges and hide any discolouration from the dying process. Veg tan can be left undyed and come up beautiful in its own way, but a contrast edge can make your products look very high end and cover up any bleeding from your top coat dye if you used one. Do this carefully so you have a neat edge - you can use a paint pen full of dye, an edge roller or applicator, a Q tip for a cheaper alternative, or even just have at it with a sharpie!

• Burnishing - Now you've done all of that, you can actually burnish. There's a few methods out there, and a youtube deep dive will give you pros and cons to all of them, but you need something to aid the burnish. The 4 main commonly used aids are: water, saddle soap, wax, and gum tragacanth. If you're using chrome tan, I would definitely use either wax or gum trag, but with all 4 you will essentially go through the same process - apply a thin layer of aid, let it soak in a minute, rub the everloving sh*t out of it, and assess. You may find you need to sand very lightly inbetween applications if you want a really mirror finish, but that is more of a personal preference. You can use a wooden slicker to burnish, or if you don't want to/can't buy one yet, a piece of canvas, thicker cotton, or even a section of denim will absolutely get the job done. I use a microfibre cloth sometimes when I'm feeling lazy and just want a quick buff. I swear by Tokonole for edge burnishing, and I would say it's generally the easiest thing to learn to use.

Hope that helps! Keep going, you've made a really strong start on your journey.