If this is your first work, then down the road you'll learn enough to be a hoot.
You have the eye, now you need some tools.
Get or make a clamp to stitch with
the top guy was made for me by the Cabinet maker in Williamsburg in 1977. The bottom guy I ppicked up at a Flea in 1999.
I judge you're using one of those stamping tools that cuts your stitching holes with a hammer., and you probably use the larger version of harness needles. That's OK but you'll work faster with an awl, marking wheel and grooving tool
You'll stitch faster with a clamp, two SMALLER harness Needles and by spending a few moments to taper the thread end so you can live with tighter stitches and smaller holes.
If you start with sinew, scrape the three inches or so at the tiop with a sharp knife, wax the snot out of it, and thread your needle with a lock
One of these days I am going to get off my fanny and string together some of the articles I wrote on cordwaining for a tutorial. I've about taken my riflemaking to its plateau of mediocrity and am starting to itch for some leather projects.
Good start, keep it up.
and
don't shoot yore eye out, kid
The Capgun Kid AKA the Still River Cordwainer