After both sides of your sponge have grout on them rinse your sponge off and repeat the process until all joints have an appropriate amount of grout.
How to grout slate floor tiles.
Once you have done this only use the other side of the sponge and only once.
Scoop a small amount of grout on a grout squeegee.
First move the grout float a specially designed smoothing tool that features a flat and mostly firm rubber pad.
2 spread the grout over a small joint.
Replace or reinstall any remaining damaged or lifted slate and let the floor dry overnight before grouting.
To avoid spreading the excess grout across your tiles use one side of the sponge to wipe along the joint.
Press the tile into the opening on the floor.
Use a grout float to press the grout into the space between tiles.
A tip for you.
Fill a plastic spray bottle or a small pump sprayer with grout and tile sealer and spray the slate tile evenly making sure to get the sealer on the inside edges of the tiles.
Scrape away any excess grout.
Scoop some grout onto the tile floor with a trowel.
It is best to use unsanded grout for slate floors.
Select an area 2 to 3 feet square to begin and apply the grout with a rubber faced trowel to spread the grout across the slates working it into the channels between the tiles.