Self levelling compounds are designed to level and smooth the sub floor and are great for use with large format tile slabs that require a very flat base. Available in single-part and two-part varieties, self levelling compounds are also ideal for use with underfloor heating to create a smooth, flat layer over the top.
Be sure to check the instructions on the pack of self levelling compound so that you prepare it correctly - this is an important part of achieving a smooth floor. The temperature and conditions that it is poured in will impact on the amount of time the product takes to dry, so factor this in to your calculations as it must be completely dry before tiling can commence.
Tile Fix Direct stocks self levelling compounds from Ardex and Norcros.