Makiing an inclined bed

I came across this site and find this interesting. I wanted to say hello and ask for some help.

I have a few health issues I am hoping it will hwlp with. The bed I have isn't in good shape so would like to make an inclined bed. Does anyone have some diagrams and instructions for this? I will use a single/twin mattress because of room size. I don't need a headboard.

I have seen some beds with slats for a base and some with plywood. What is the difference in purpose of these?

Most of the homemade beds I've seen come without a box spring, so I am wondering what the purpose is of using a boxspring?

Joe