I recently made a forge/ foundry, and have melted down some aluminum pop cans. I made a ingot, but it wasn't that big. I have a friend that made a mold for making a ring, but he decided to keep it at his place so i didn't use a mold. I just cut it the ingot until I got what was close to about a rectangle. I made it a rectangle because my finders are more rectangle than circle(and some other reasons).
Tools used where:
Dremel-with about 5 different bits
Drill- with drill bits
I have put about 2 or so hours into it. Maybe closer to 3.