If you ever tried to build a door, you will probably realize that a flimsy door isn’t worth the time or effort. At the same time, a sturdy door can weigh so much that using the door in its intended place might not be ideal (I once build a playhouse door that could have severed fingers. This required a same day redo so that there weren’t injured toddlers everywhere. A dutch door no less. A dutch door is just asking to be slammed to keep the other kids out)
Back to the door. A proper door is just the right amount of strength and weight and the following Board and Batten door plan hits the mark. Some folks assume that the diagonal pieces that are part of the “design” of the door are just that… design elements. They are not. The diagonal parts transfer the natural force that causes a door to rack and sag and transfers that force to the strong points… the hinges. When building your door, please keep in mind that the diagonals need to be placed in the proper direction to transfer the load.
Good luck building your own door. These make fantastic sliding doors (see Pinterest) that are all the rage nowadays.
The full door plans can be found on Extreme How To. Good luck, have fun, and be safe.