This is a very bright spotlight, too bright sometimes.
A diffuser I added to mellow it out. However, more mellowing was needed.
Picture if you will the very 3D shape of what I cut from this old PET bottle.
Since I wanted a flat disk I put it in the oven (cookie sheet with parchment paper) at maybe 250F. That softened it up and maybe would have been good enough. I wasn't sure so I bumped it up to 300 or maybe 350 which turned out to be a bit too much, the edges started to melt.
Then I attempted to squash it flat between two cookie sheets and got what you see below.