Hi AliMusa,
Most platform beds don’t need a foundation but you can still add a foundation on top of the slats as an option if you prefer the extra height.
You could also add some risers under the legs of your bedframe (see here for some examples).
A layer of ultra firm foam on top of the slats under your mattress (the firmer the better so that it doesn’t compromise the support under your mattress) can also add some extra height.
You could also use taller legs or adjustable legs under a steel bedframe or you could use taller legs attached directly under a foundation (see post #8 here).
You could also build your own platform bed and customize the height to your preferences as well. There are some DIY platform bed designs linked near the end of post #1 here.
Phoenix