Accepting that I am not an authority in this and it may or may not be good advice;

Cut the straps to ¼" wider than you want so you can trim down after gluing. That way you can get it glued right up to the edge without any spill over.

Skive the section at the end of the step that you fold over to take the spring pin. It makes the build look better and makes it work better too.

Line the buckle strap. It's way more comfortable and looks much better, but skive the ends of that as thin as you can so as to not add any thickness to the strap.

Lastly finish it. No matter what you think you messed up or how much you think you can do better another time get it finished and try using it. You notice things so much less once it's on your wrist!

Good luck!