We are going to start laying a slate floor today, my husband will be fine hes quite confident about doing it but the question we need to ask is this: because it is natural slate the thickness varies does he keep it level on the floor by using deeper levels of adhesive where needed or is it normal and natural to be left with an uneven floor due to the nature of the product?
Yes, that is the way to do it, if you don't, then the results are horrendous. Some of the badly laid slate floors i've seen are both awful and dangerous.
As Top Gooner says. The job is not as easy as putting down concrete paving slabs (which are the same thickness) because you have to adjust the thickness of the bed underneath to suit the different thickness of each natural slate. It'll look good once you've done it though.