I'm trying to hang a bifold door in the entrance to my bedroom but the walls are crooked. I have a small studio and wanted more privacy but didn't want a door that opens up to save space. We are using 2X4's to fill in the space since the door is 3 inches smaller than the space.In the process of hanging the door we found the space is one inch wider at the ceiling than the floor. We have a 1 inch gap due to the crooked wall. How can we fill that gap? Keep in mind I'm trying to keep this a inexpensive do it myself project that is by no means professional and I don't want to hire someone if possible