I needed a cover for the trap door box in the left corner in that back. It is a pretty odd shape. I made it easy on myself for a change. I just covered the area in duct tape.

Then I wetted out a previous template size of 2 ply BID on foil. I covered the area, let it cure and then released the glass as you can see in pic 2.

Pic 3 is after a quick clean up and I now have a perfectly fitting cover that solves the intrusion in the corner issue.

Tape the shape

Glass the shape

Use the shape