Advice/ Suggestions on a DIY Seed Growing Mat

I need some advice or input on an idea of making a very large heated seed growing mat. I have a queen-sized electric blanket that we no longer use & was wondering if I could spread it out on a table (old door on plastic milk crates) & then cover it with a plastic tablecloth. I have some plastic nursery seed trays and would find something to set them in to catch the water drainage. I plan on setting it up in my storage shed since there's no room & not enough sunlight in the house. What ya'll think???? Anybody??? Pin It