I thought about building a platform for years to have a more permanent bed in the car and a global pandemic finally gave me the time and push to get it done haha. I remember even getting someones plans back when I was living in MT years ago simply with the idea of adding storage for skis, etc under it. For all plans, keep in mind I have limited construction skills but took notes along the way to hope to inspire others with little experience and a shared love for spontaneous camping to do the same :)
First, I went to my local Home Depot and bought a 3/4" plywood and cut it to 53" at the store to help it fit in my car. This is what I measured the width of my 2015 Jeep Wrangler to be. I later decided I wanted 8" height of storage which changed the back width to 43" due to the molding over the tires so had to make some adjustments. I bought 2 pieces of plywood so had room for mistakes ;)
For the supports, I was a little impulsive and just built some supports without thinking too hard about it. I bought a 3" memory foam topper off Amazon and a waterproof cover and flannel sheets from Target (full size). The platform was built into 3 pieces. The back piece had the supports for storage, the middle part was the distance from the trunk essentially to the front seats when upright and then a front piece that was piano hinged so the bed could be extended to maximum length for sleeping by sliding the front seats forward.
The next week, Zax and I took it out and I quickly bought another pillow top cover to make it more comfortable and later ended up adding my self-inflating pad under the mattress to add that much more cushion.
As the end of February approached, I had help building a drawer by my friend, now boyfriend, Jeremy haha apparently building a drawer is the way to a girls heart. I decided to readjust the supports for the drawer to make a 28" long x 16" wide drawer to better accommodate kitchen area. We put drawer sliders on and built a lid with a piano hinge. We hung the pieces to varnish. Jeremy came up with the creative idea of putting hooks on the ceiling of the garage so we could paint all the sides at once and that worked great for us. We did 3 coats of Rustoleum varnish that requires 6hr between coats.
After it was ready, we put it all together and put handles on both the top drawer and slide out piece for the sink. We were worried about the weight when extended so added retractable locking straps to hold it down with hardware in the Jeep for it to connect to. I added a latch to connect the back and middle pieces as well. We had another pull out under the drawer to be used as another surface for cutting/ materials and also cut out a piece with the option to put a sink area in which we haven't used.