Buying a King size Latex from Sleep EZ, through one of the companies that picks up trial bed returns and have a question regarding the proper support for it. We have a King bed with rails and slats for a box springs. I gather box springs are not appropriate for the king latex mattress.
Will a platform foundation fit inside of the wooden bed/frame? or is there a foundation that would rest on the bed frame rails? Bonus points for links to what I need. 
Thanks!
Most foundations should fit. One excellent foundation is terra foundation without the legs. It will fit right on top of the bed frame you have. Another option is a zero clearance adjustable base. That will fit right on the cross slats of the bed-frame.
Just be certain you have center leg supports on your bed-frame.
This is similar to my set up. I have a bed-frame with headboard and foot-board, side boards with about 6-8 cross slats to hold the bed-frame secure. I placed my wooden box foundation directly on top of those cross slats, which also have additional center support legs for additional stability.
Maverick