FREE ESPEVÄR standalone bed (no headboard)/ Slatted mattress base / box spring compatible with all ikea beds - RRP $250

https://www.ikea.com/us/en/p/espevaer-slatted-mattress-base-for-bed-frame-dark-gray-s19156586/

Comes with free LYNGÖR white cover - RRP $40.

You can add BURFJORD or BRENNÅSEN legs from Ikea to raise it off floor

It is fully assembled and you would need to collect from Oak Creek Apartments next to Stanford campus.