During my 2015 Prius travels I camped a number of times in the desert and camping spots without a picnic table and I had a couple of problems cooking.
First, I needed a wind break for my butane cooking stove so I set up on the leeward side and opened the door and had a nice spot to cook out of the wind. I cooked off the very small roll-up camp table.
Second, I didn't have a place to prepare the rest of the food and dishes as the little table I carry wasn't big enough. I resorted to using the top of the fridge as a flat surface under the rear hatch. There was too much moving back and forth around the car. Although good for exercise it was not good for cooking and eating.
This modification wasn't high on my list but it was so simple and gives me a nice level surface for eating and working on small projects.
I always start out with a cardboard scribed with a compass to give me the angles and create a template before cutting wood.
I then traced the cardboard template onto lauan plywood and cut it out.
Then I needed to make a brace on one end to keep the table from sliding up on the side with the door pin as the other side of the table is pressure fit. For the brace I decided to use 5/4" plastic wood and miter the bottom where it touches the table and put shoulders on the part that goes into door pin. The length from the miter to the door pin is sized to give a level table top.
The table is reversible so it can be used on the drivers side rear door too. You just need to flip it over as the other side of the Prius is a mirror image.
I will primarily use the table on the passenger side (above photo) as this is where the cooking pots and pans, utensils, and dry food and water are stored.
It works out that the table will slide in the storage area under the bed where my camp cooking items are. Since it is only an 1/8" it doesn't use up too much room.
The lauan at an 1/8" is sturdy enough, for cooking with a pot of water or for using as a table for my plate of food and drink, but to increase strength and possible sagging that could occur over time I glued stiffening bead to one side. I made the bead by cutting off the bull nose I made on my router.
After the Prius door table is sealed with multiple coats of polyurethane it will be ready for my 2016 travels.