We used to have the king size frame, box spring, and mattress as our bed (we slept without any headboard for years, people!) when we were in Arkansas. Moving to Clemson, we only took the mattress with us (just couldn't let it go because it is way too comfortable!) The new bed we purchased later is builded to go with the box spring, and then mattress. Oopss!! we have no box spring!! We live with it for almost a year now and there was always a gap at the top of our head (the space that should be covered with a box spring on).
Bed with gap
Despite the gap, we are very happy with the height of our bed. We are those people that do not like to climb on the bed every night to sleep, and most importantly, we have kids who like jumping in and out of bed hundred times a day.. we just don't want them to get hurt (or tired??!!)
I hate that gap at our headboard so much. Sophia dropped through that gap 3 times already. She got stuck and cried. We had to move the bed to get her out of there. And every night, I was sleeping worried sh*t that she might fall down through the gap. We later put a lot of pillows there but it was just temporary. Anyway, we planned and planned, and today is the day that the gap is forever GONE!
I upholstered a panel to fill the gap. It is pretty similar to making an upholstered bench, don't you think?
Fabric: $6 (and plenty leftover)
Foam: $10 (we used foam mattress topper from Walmart to cut costs)
2x10x6 Top Choice Pine Wood foamed up with mattress topper. Leave extra foam at sides to soften edges
Hot glued foam to wood panel
Stapled fabric to the panel (I skipped wrapping with batting, but I would if it is a bench)
Make sure the fabric pulled evenly
and attached it to the headboard. Tada!!