Four day work week sounds great, but how do you prevent employers from taking advantage of that and saying, "Hey, as an hourly employee working four days a week

Four day work week sounds great, but how do you prevent employers from taking advantage of that and saying, "Hey, as an hourly employee working four days a week, we don't have to cover your insurance because reasons". I'm sure there are a lot of loopholes or rules that companies can't wait to exploit to pay people less money or fork over less money overall.