I did a little experimenting. First off, I think it's important to sit in a chair (rather than a sofa) where you can rest your elbows. Second, I noticed that the sewing case I bought from Walmart would work very nicely as a raised, padded surface to work on. It's about 7" tall and sits in my lap. I could add a strip of wood or styrofoam to the back bottom so that it would tilt, and this would create a nice raised surface where I could work with my wrists in a neutral position. A neutral position for wrists means that they are not bent, but rather are kept nice and straight. This prevents repetitive stress injury that results in carpal tunnel syndrome.
Here's a link to the type of sewing case I mean:
https://www.walmart.com/ip/Deluxe-Se...White/50654209
Walmart has them in their sewing section, and JoAnn Fabrics always carries a selection too. Mine has a padded wooden top that would be easy to work on, and for tilt all I would need to do is glue or velcro something under one edge of the bottom so the top would face towards me when on my lap.
I should add that my sewing case has a hard cover and latches. Those with zippers are probably soft covers. You could still use one by filling the box with styrofoam, but I think it would be easier to just get one with a padded wood cover.