I put four single-flat sized heating mats (with a controller) along the raised back part of my kitchen island several years ago when I had a lot of bettas. They've gradually died off (of old age), and now I have just 3. That means I have at least 2 heating mats available for rooting cuttings and starting seeds! It's easy to watch for those first sprouts when they aren't popping up in flats in the basement.
I do have 2 flats in the basement now, mostly tomato seedlings and a handful of basil. These tomatoes will be planted out with protection in April. In a couple weeks, I'll start another round of tomato seedlings, timed for hardening off the week before the swap. I'll need to figure out garden space for them (might just try tucking 2 here, 2 there), but I won't be keeping more than 2 of each kind, and you KNOW I'll sow more than 2 seeds... So, I should have a good selection of OP tomatoes at the swap.