I make them in various ways. I started off adding handles to blades I bought and making sheaths for them. Since then I either forge from scrap metal such as leaf springs and railroad spikes or whatever I get hold of and grind to the finished shape or grind to shape without forging.
Some examples ...
Made from an old wrench.
Forging a bowie.
Leaf springs make good blades.
Currently working on a Seax.
The blade is forged from a piece of leaf spring and I've started to grind it to the final shape.
Next will be heat treating and tempering, add a handle and make a sheath.
Some of my equipment.