Mix it all together in a bowl. Add the water last, a little at a time. Depending on your flour you might not be able to get that much water to absorb into the dough, so just add add much as you can.
Knead it a bit. I try to stretch the fibers by rolling the dough into a sausage shape and then folding in half. Repeat. I believe that this helps the gluten to align in one direction kind of like muscle fibers. That's just a guess though.
The more you knead the tougher your finished seitan will be. I like to go easy on it so the finished product has a texture more like tender meat. After you are done kneading, leave it for a few hours to relax or something.
Slice the dough into 4 chicken breast sized pieces (mine has quite an authentic raw meat texture at this point) and marinade in a BBQ sauce of your choosing (about 1 hour marinade worked for me, but longer is always better).
Grill it on the BBQ. Brush more BBQ sauce into the steaks as they are cooking. Slice into strips. Dip the strips in more sauce if required. Add to pizza/fajitas/bibimbap etc.