Some will advise you back butter the tiles & this might be a good idea if you use the smaller trowel but back buttering will make it more difficult for you to level the tiles & if you use the correct size trowel in the first place, it’s rarely necessary.
All the floor trowels I’ve used are around 11" or 28cm & if you think about it, the size compatible with 300mm tiles; but I lay down about a square metre of addy at a time anyway.
All the floor trowels I’ve used are around 11" or 28cm & if you think about it, the size compatible with 300mm tiles; but I lay down about a square metre of addy at a time anyway.