Blocking mats

The first time I saw a knitting tool like this - a blocking mat - I thought: How smart, they use the kids play mat for blocking their knits. I didn't know that mats like these are actually sold as knitting tools. I want one! I like the KnitPicks set with which you can put together as many pieces as you need so it's easy to store. But I assume that those foam mats that you can buy for kids room will work well too and might be cheaper to buy. I also heard you can use a yoga mat with the same result. I've used the iron board so far but it doesn't really work well with larger pieces. If you don't have mats like these, what do you use?