I use one of those pillows (
https://www.amazon.it/-/en/Purovi-Er.../dp/B011INGXFS /
https://www.amazon.it/dp/B06XHT9GRV/ ), in its vertical stance, so I can bend the legs and lean the e-reader, or the book, on the thighs/knees.
But lately reading almost on a chair, which swings and can put the foots on a pouf.