DIY Training Platforms

[Raegan]

I want to build some platforms because I haven't found anything that meets my needs and isn't prohibitively expensive. I'm a little unsure about how to go about it and was hoping you all could help me brainstorm. Here's what I need:

- aprox 18" x 24" x 3"
- won't slide on variable surfaces (carpet, snow, grass, etc) when hit by a dog at speed
- comfortable enough to sit on for up to 3 minutes.
- reasonably portable, 90% of the time I'll have to haul them around and set them up myself.
-at least 4, 5-6 would be better

Something like this would be good, but it's taller than I would like:


I've thought about just making wood boxes, but I don't have easy access to power tools (particularly a saw, I could borrow a drill pretty easy) and I'm worried they'll be too heavy for practical use.


Foam is probably too light:


Any ideas?