At this stage, leatherworking is the same as it's been since vegetable tanned leather reached high enough quality to permit tooling (sometime during the roman empire). I'll be describing each stage to go from a side of leather to a finished item and each new article should come out every other day or so.
We begin with a side of veg-tan leather and some cutting implements. As the name implies, veg-tan leather is leather that's been tanned using vegetable matter, generally oak or hemlock, which contains large amounts of tannin. This process produces a leather that takes and holds impressions quite well and burnishes nicely. It's definitely the defacto "canvas" for leather carving.
I use a tool called a strap cutter to slice 1" wide strips off the long side of the side. In this case I needed to wind up with about 50 1"x5.5" pieces so some simple math tells me I needed about ~300" of strap. Sides vary in length but mine was about 40" or so wide, at least where I was going to be cutting. The leather does originally come from a living creature so it's not uncommon for it to have blemishes or holes that need to be cut around so in the end I figured I needed about 8-8.5 straps to get all the pieces I needed.
Once I had the straps cut I used a very sharp trim knife and a square to cut the bits to length. By the time I was done I had 51 rectangular pieces of leather that were all 1" x 5.5" but they're still what I like to call "rough cut". So in order to clean them up a bit I used an old woodworking tool I've kept around to round out all of the corners. I have wood forms and knives specifically for rounding larger corners but for little bits like this I find this old gouge works pretty perfectly.