Now you need to purchase a new inner sole.

If you found one which is the same size as your old one, you can skip the next step. But many replacement inner soles need to be cut to size.

Place the old inner sole on top of the replacement material.

Trace its outline with a pen or marker onto the new material

Take care: Keep both new and old inner soles facing upside-down, so that you mark on the bottom side, and that after cutting, the correct side faces up