Slats are a great option. Slats should be the same width, flat and spaced equidistant from each other, no more than 3" apart.
Keep in mind that the Leesa and Leesa Hybrid mattress should be set up on a flat, rigid surface. Some slats are bowed or flexible which can change the way a foam mattress is intended to feel and aren't recommended. Using bowed or flexible slats with your Leesa or Leesa Hybrid mattress can cause damage and can void our 10-year warranty.