304 is not hardenable. While it would work, any martensitic stainless would be a better choice. An unhardened edge will microscopically round fast and not scrape as cleanly or efficiently. This will require constant burnishing of the edge to keep a slight burr and regular re-flattening of teh edge to create a new burr.
AEB-L, CPM154, 440C would all be cheap and easy.
You can get the bar hardened by many knifemakers. I'm sure several folks here would be glad to do it for you. You didn't fill out your profile, so we don't know where you live, but someone local might be glad to harden a bar and give it to you.
I have made quite a few scrapers/fleshers. I usually use 1095 or W2 for the Buckskinner folks because it is traditional patina. I harden the bar and then grind the edge bevels. For stainless I use 440C or CPM-154 (or any bar of stainless I have sitting around that's the right size).
For folks who want a cheap scraper, they often use old planer blades, as the blades can be found for free from woodworkers. In either case the blade is from a hardened steel.
A really good choice is an old draw knife from a yard sale. They are almost always some steel like W2. You can often find one at a yard sale for $1 with a missing handle. All you need to do is regrind the edge and fix the handle. I have re-forged the handle tangs to be at a lesser angle for use as a scraper. You can make the handles from fancy wood on the lathe, or an old tee-shirt and duct tape .... they would both do the same job.
The way I make them is to take a 16" straight bar of steel and flatten/clean all sides to 120 grit. I round both ends so they are smooth and sharpen the middle 8" section on the top and bottom edges at negative 1°. Just barely tilt the bar back from vertical and make a few passes ... done! You can use a fine stone and/or a hone to make it very smooth and create a crisp edge if you want, but 120 grit does just fine and takes only seconds to restore on the grinder.
They call it a 91° edge because you use the side with the forward edge exposed. You don't need to be all that critical about what the angle actually is, just that it has a very slight angle to both narrow sides. 91° to 100° will all work fine. You want this style edge as clean and smooth as possible with no rounding. This allows the flesher to be scraped along the wet hide with no chance of digging in, but grabs all the flesh and such cleanly to remove it and clean the hide. You can experiment with grinding the edges at angles up to 100° to see what works best for your style of fleshing. It is nice to have one edge at 91L and the opposite one at 95° to 100°. This allows more aggressive work at a thick area or a place with extra flesh still attached.
If you can't find a nearby knifemaker or get what you need and want a hardened and beveled bar, I'd be glad to make you one and send it to you if you are in the 48 states.
