I used this today for cutting shingles, but you can use it anywhere you need to cut something like floor tiles or a Model T floor mat to fit an odd-shaped space.
Cut strips of corrugated box or stiff cardboard, lay them along the edges of the space you're filling, and tape them together to make a template.
Use the template to mark the piece you're going to cut.
That last weird piece (left center) fits right in.
Steve, that same principle works when cutting floor mats for the T. I use quarto size card and lay the straight edges where they fit, and then cut the odd ones shape. Tape the whole lot together securely, and the assembly can be lifted out for use as the pattern.
Hope this helps.
Allan from down under.