Hi basily,
The foundation post here and the posts it links to has more information about the types of foundations or other support surfaces that are generally suitable for different types of mattresses. A gap between the slats that is 3" (or preferably less) with 1" x 3" slats (which are actually .75" x 2.5" when they are finished) is a good guideline for mattresses that have a latex support core. It’s usually a good idea to have a support surface that is about 50% of the total surface area of the support surface so if you use thinner slats then I would use smaller gaps so you have a stronger and more evenly supportive surface.
Phoenix