That's a good idea! I'll try that next time, it looks more solid than mine
I made my own germination mat the other day. I looked at prices for heat mats, and decided be creative and save some bucks, since I went waaay over my budget this month (Holidays!
Taped and (carefully) stapled some cheap indoors christmas lights on a piece of coroplast (those electoral banners), then put it at the bottom of an aquarium. Covered everything with clean sand, then foil paper. One half of the Christmas light pad heats to 25-28C, and the other half to 20C.
My seeds are in seedling mix in a Ferrero Rocher box. Hopes it works!