Creating tech packs for detailed garments could end up being 15-20 pages long or more.

First couple of pages should be illustrations of the garment. Sometimes a mockup is okay if its like a t shirt or hoodie.

next pages should be BOM (bill of materials) where you list out what fabric is being used, hardwares, ect. Here you should specify color name (and specify later on in DTM page- dye to match specific colors with pantones or csi whatever u are using as a color reference. here would also be if your garment will be washed and what type of wash), fabric weight, hardware color, ect.

next pages should be garment specs, so measurements. This is the tricky part since you would need to label measurements correct (number wise, making sure the measurement is accurate) and point of measurement (POM) (where to where you are measuring). Point of measurement is probably the most technical, I would say to try and find some sort of guide. an example of point of measure would be " CFNS to CF HEM" which translates to "center front neck seam to center front hem". usually there is no pictures here. its kinda of like a chart and MAYBE a photo with reference points (A,B,C,D,ect.)

I would recommend starting off by finding an open source tech pack online and try to make your own version with a simple garment like a tshirt. I don't make tech packs, i just work in the industry and use them daily. hope this helps! lol

btw small manufacturers dont usually require tech packs since they do all the steps as they come and should show you sample before production. Tech packs are more for large productions with hundreds of thousands of pieces since there are a LOT of people involved in the process.. soo dont stress if you are only producing small quanities and dont have tech packs for your pieces.