I'd leave them in the box for a few days. I'd also prepare a box on the floor of the coop for when they decide it is time to take that first leap! Once one goes, the rest will follow. Then, they'll have new digs waiting for them.
Yup... Cuz they won't get back up... I always place my broody on the floor when the chicks hatch, in a nest box. Then of course, you get a broody like mine who took her babies out side when they were 3 days old! Now I have to set her box on the ground, and when they all go in,I pick it up and set it back in the coop.