Courtesy of Richard E. MT
When it comes time to sprout seeds, it is warm enough that I don't need my electric blanket so I use it for seeds. I fold it to fit the space needed and cover with plastic or tarp. I do it in my basement and turn off the blanket when seeds are sprouted, after about 7-10 days. Ambient temp is about 55 degrees.
I put up shelves out of scrap lumber using screws so it is easy to disassemble and store. The bottom of each shelf supports a light on a small chain to make it easy to adjust for the shelf under it. The secret is bright light so you don't get spindly plants. I start about 1,152 plants, mostly tomatoes and peppers, this way and it has worked well for us. The cool ambient temp makes hardening of the plants easy as you put them outside.