Collect a bunch of miscellaneous things - empty film cannisters, straws, metal washers, clothespins, whatever you have or can find that's relatively small.
Put it all in a bag, then give it to him with the instructions that he is to make ONE THING, using ALL THE PARTS IN THE BAG. The only thing he can add is paint and glue.
Definitely develops imagination and creativity!
Failing that, I suggest you make your son responsible for finding ways to cure his boredom (other than sitting in front of an electronic device). If he's a kindergartner, he's around age 5.
Five year olds can find something to occupy their time - if he can't, then I suggest you allow him to help you around the house with dishes, laundry, vacuuming and so on. That should clear up his boredom real fast.
