A 800×400mm toy box on locking casters, 400mm tall to a child's hand level. The hinged lid is sized to overlap the box on three sides for a clean look and to hide a slow-close hinge so kids can't slam fingers in it — non-negotiable on this build. Casters let the box roll under a window or out for play and tuck back at bedtime.
Round every external edge with a 6mm roundover bit. Drill ventilation holes near the top of one short side — an old kid-safety standard, in case a child climbs inside and the lid closes. Finish with low-VOC water-based poly so the box doesn't off-gas in a kid's room.