For example, learning how to play an instrument, picking up painting, attempting to master chess, or Go, are all things that you could do instead of working and are still personally enriching, if not financially enriching. They may not boost the economy directly but they will make the culture a better place nonetheless. There is a lot of untapped potential that could be explored if people have a guaranteed basic income and didn't have to work that dead-end, minimum-wage job.
Of course we still need a lot of human labour to make society run. I mean who wants to do menial labour, or plough snow at 4am so the morning commute isn't a complete disaster.
So I don't have an answer, I just think you're falsely equating "not working" with "idle hands".
What gives you more self-worth, learning a new programming language and completing a project in it, or sitting on the couch and watching TV?
I personally believe the ancients understood this, from the usual parables. Idle hands are of the devil, and lead you to fill your time with something. Most of the easy somethings are drinking, eating and junk entertainment.
Technology may give us less to do, but at the expense of less opportunities for developing self worth. Even some of the founding computer members understood this--Wiener, a member of the "Dream Machine" crew mentioned it in the book "Cybernetics".
Perhaps I may clarify the historical background of the present situation if I say that the first industrial revolution, the revolution of the “dark satanic mills,” was the devaluation of the human arm by the competition of machinery. . . . The modern industrial revolution [i.e., the computer revolution] is similarly bound to devalue the human brain. . . . The answer, of course, is to have a society based on human values other than buying and selling. To arrive at this society, we need a good deal of planning and a good deal of struggle. . . . (Wiener, 1948, pp. 37-38, bracketed words added)