Steps to make something out of leather?

[Retswerb]

Nothing wrong with that, all part of the process sometimes. Use fabric, paper, scraps, whatever it takes to figure out how the pieces are going to fit together to give you the result you want.

[Danne]

I would recommend you to start with smaller items. Even if it's just test pieces. Because when you start to make bags, mistakes cost a decent amount of money because of the amount of leather.

Someone asked me something along the line "How is it possible you have improved so much but not made a lot of things" (Keep in mind I do wallets and watch straps and small things) and I haven't done a lot of finished products, but I have done A LOT of small pieces. Like glue together two small scrap pieces, stitch it, crease it, bevel the edge and paint the edge. This way I now I feel confident in the techniques needed when I make that wallet or watch strap. Sure a watch strap is very little material cost, but it's not fun spending hours on a watch strap and making a mistake that ruin it because I lack experience of a certain technique. 

So in your case, I would use scrap leather and do test pieces of bag corners, maybe if you use zippers, just take two smaller pieces of scrap leather and stitch in a small zipper. Maybe the next step can be to make a dopp kit?