Looking for slippers where the insides don’t flatten

Hello! I’ve gone through 2 pairs of $30-$40 slippers so far and i’ve had an issue with them i’m looking to get something better. after a year with the first pair the inside of the slippers where your feet go in, the wool cushioning keeps flattening and is unable to bring back to life. for the second pair i made sure they were machine wash but it hasn’t help. so i was hoping to get some recs on slippers where the soft part your foot lies on/in doesn’t flatten and get unsoft/flattened? i don’t care for it to be wool or anything specific, just something soft with cushioning within the shoe!