Don't overwork them, don't be unreasonable towards them, don't disrespect them and pay them a living wage to do some sort of meaningful work (e.g. care work).
This isn't that hard. The US has done it before.
>And how do you finance it?
There's a hundred different ways.
>With a UBI you don't have to pay as much
You have to pay more because it goes to everybody instead of just the unemployed and you don't get anything in return for that money.
>What if 85% of people choose the "basic job"
That's kind of like asking "what if programmers all gave up their jobs at once to become cleaners?".
> the only way to change that is to either make the "basic job" degrading
A "basic job" can establish a floor on job quality and wages. Private employers will respond to this market force by paying more and treating people better and they will complain bitterly about it.
And how do you finance it? With a UBI you don't have to pay as much because people can supplement it with an actual job even if pays less than current minimum wage, and everyone who works is offsetting part or all of their own cost by paying taxes. 100% of people can collect the UBI because most of them will still be working and paying taxes, and if they don't it's only because the amount is too high.
What if 85% of people choose the "basic job", and the only way to change that is to either make the "basic job" degrading or have it pay less than a living wage?