Back in the days when I made extensive use of a laptop computer, I found resting it on my actual lap while I was working on the sofa to be pretty damned uncomfortable, not least because of all the heat it put out. So I took to resting an old wooden chopping board across my knees to act as a table-cum-heat-shield. It worked really well.
When I’d been using this arrangement for a couple of years, I was delighted to come across the following passage in the Reminiscences of his father by Charles Darwin’s son Francis:
After he had read his paper, came his time for writing letters. These, as well as the MS. of his books, were written by him as he sat in a huge horse-hair chair by the fire, his paper supported on a board resting on the arms of the chair.
A pleasing example, I like to think, of great minds thinking alike!
After I replaced my laptop PC with an iPad and keyboard, heat was no longer a problem, but the keyboard wasn’t rigid enough to rest on my lap directly, so I migrated to a smaller, thinner plastic chopping board. Again, this worked—and continues to work—very well.

Under this new arrangement, my large wooden chopping board was temporarily retired. Recently, however, I found a new use for it, acting as a makeshift laptop desk while I’m sitting in my reading armchair in my study. I read a lot of physically heavy hardback factual books, routinely making notes about them on index-card bookmarks. Resting the book and cards on the chopping board placed across my knees has made such note-making that much easier. Better still, I’ve also taken to laying an old piece of cloth across the board to provide some extra protection for the book. I wrap the book in the same cloth whenever I take a break from reading. This might sound like an unnecessarily elaborate, possibly ostentatious set-up, but it works an absolute treat.

This year, my reading has mostly centred around the Correspondence of Charles Darwin. I have to admit, I get a big kick out of reading and making notes on letters my hero wrote in his study on a board placed across the arms of his chair using a similar board in my own study.