I started many years ago meditation using a zen zafu, but then I realized that it was difficult for me to remain in the same posture for long because my butt hurt. After that I used common cushions and they were softer and better. However after a 10-day retreat and 10 hours of meditation each day sitting in a foam cushion, I can say that I have found the perfect cushion for me to achieve stillness in asana, because my butt didn't hurt not even once.
I use: - instead of a zafuton I use 1 unit of foam of 70x90x7 cm - instead of a zafu (on top of the zafuton) I use: 1 unit of foam of 45x30x10 cm 2 units of foam of 45x30x5 cm According to your weight and constitution add or quit or change the height as you need. My wife only needs the zafuton and then 1 unit of foam of 45x30x10 cm.
Thanks. With asanas I meant sitting asanas, like Siddhasana. I got them at a local store where they sell materials for cushions. They cut them with the measurements that I gave them.