I had a door desk in college. It was solid core with a flat surface. You could buy them at a deep discount if you found one with surface defects. I used cinder

I had a door desk in college. It was solid core with a flat surface. You could buy them at a deep discount if you found one with surface defects. I used cinder blocks to support the corners, making it cheap and portable. Simply put, it was the best desk I have ever had.