KrOnk. The link I gave you in another thread had pics, but probably not enough info to show how to do this. Here's how I'm going to do mine(Same as all my other stuff, just a different piece);
Cut an oversized triangular piece of your material(about one inch larger on both sides, and at each end).
Using a ball pein(sometimes written "peen") hammer, hammer out a depression in the end-grain of a dry stump or bury a chunk of log or telephone pole. Just pounding heck out of the wood will creata a nice bowl effect. It will also make the wood denser and stronger there. Hammer it smooth.
With your ball pein hammer's rounded end(they can be purchased for cheap; way less than ten bucks), start working the metal over the depression. Not whacking, but not tapping. Enough to change it. Start at the outside and work in to the center. If you picture it as a clock, work from 12 to 3, then 12 to 9, then 6 to 3, then 6 to 9. This will keep it from taking on a spiral twist.
Don't worry about getting a finished shape the first time around, but try not to strike more than you have to. Aluminum actually gets harder as you work it(read; brittle)repeatedly. You really don't want to have to anneal it to soften it up. Just work steadily, and you should have it pretty well done in three times around.
If there are alot of uneven raised parts, use the pein to tap tap tap very quickly and close together on that smoothed post to even the surface out. Don't strike, just tap. You'll see what I mean as you try it. Trim off any extra.
Finally, sand the surface lightly, then wash with hot water and soap. When dry, apply a couple coats of sandable spray primer, sand down the high spots, repeat as needed to get a uniform surface. Paint 'er up.
For a first timer, I would really advise practicing on a piece of scrap to get the feel of it first. Make an ashtray or something.
Hope this helped.
uke 
