For this instructable you will need:
A Red Bull can or just can bottom
Tin Snips or Scissors
Pliers (Preferably long-nosed pliers)
Like 3 minutes...
Step 1: Cut the bottom end off of a can
Further trim this edge so that the circle is even all the way round. This will keep the disk balanced.
Step 2: Bend the edges
Bend the edge down so that it follows the curvature of the dome. Once you have done this, bend it more inward " <__> "
Then, simply clamp the edge down to touch dome. Follow this through evenly for the entire rim. Fix any "unbalanced looking" edges so that the finished product is as circular as possible.