Empty soda can
Some playdoh (or any suitable replacement)
Step 1: Cutting up the can
As you can see in the picture, I had already started cutting the top of the can.
Now you have an empty can and its top. Dispose of the can top.
Step 2: Bending the rim
If there are any deformities still present, use your judgement to press and squeeze (the can) to make it as round as possible.