We built this sleeping platform for a Toyota Tundra with a camper shell and bed liner in around 4 hours with minimal tools and cost. We repurposed plywood from some old shelves and purchased one 16 ft. 2x4.
The 2x4 was cut into several pieces to make 3 supports for the platform using the smaller pieces as spacers to raise the platform to the desired height.
Because the plywood used was only 1/2" thick, we doubled it up and screwed it together. 5/8" would have been ideal, but 1/2" was all we had available.
The plywood was cut at the corners to fit snugly into the bed of the truck. If its not a tight fit, your car keys, flashlight and other small gear will fall down through the cracks at night.
Here we checked to make sure our gear would fit under the platform.
An extra support was added at the end of the truck. This end required more support because its where we climbed in and out. The first 2x4 support was close enough to the front of the truck that we didn't need to add one there.
We built a full length drawer for the left side of the bed, with the right side being used for toolbags, pelican boxes, camp chairs, etc. The plywood dividers are removable and create compartments to help organize gear. Pieces of 2x4 were used to reinforce the drawer and create slots to hold the dividers.
The drawer is 1" shorter than the truck bed length, so we used a piece of sleeping pad to fill the gap when closed and help prevent movement.
Thin pieces of plywood were cut and attached to the bottom of the drawer. The wood fit into the grooves of the bed liner and was used instead of rollers. The wood on both sides of our drawer fit into the grooves, but you could get away with only having them on one side of the drawer and still keep the drawer in place.