yes, a cushion, but every one I’ve found is too big and doesn’t fir my backpack where I have more stuff (clothes, an umbrella…).
I like doing yoga and stretching outdoors, so the ground may also have loose dirt, broken pebbles and grass…
If I bend on my fours, raise-stretch a leg with the other leg’s knee touching the ground to hold most of my weight with this leg’s foot stretched to the back and still touching the ground, raise-stretching one arm and only using the other arm not to fall to the ground, the knee touching the ground hurts.
I’ve tried folding a small towel three times, but I’m so skinny that my knee still hurts.
Folding a yoga mat doesn’t help either.
What works for you?
Depends on the type of yoga mat! Some are very thick, some are very thin. Sounds like you got one of the thinner ones. You couldn’t possibly fold one the thick ones, it would open up on its own without a weight on it whereas the thin ones can stay as you leave them.
A kneepad is another option as many said already.
You also have mats for camping, my parents had a couple of these and they would lay them under the sleeping bags precisely to avoid feeling all the debris on the ground.