Need advice on bed assembly

[Mr Chevorlet]

Hey guys i have bought used bed sides and a front panel and all the cross members for a wood bed. I was going to paint each peice seperatly then assemble, But i noticed that the bed sides set on the wood after assemble, I am not sure how to go about putting it back together after painted. My question is should i assemble before i paint. but i do not want the wood in place before i paint.

Cross members set on frame
wood sets on crossmembers
bed sides set on wood

when people replace wood how do they keep the bed in place.

Any suggestions Thanks