While the smaller tiles that make up the mosaic will be more forgiving of a gradually sloping substrate, such as the floor of a shower, it is still important to ensure the surface you're tiling onto is clean, dry and flat. Patch any holes or cracks. If the surface beneath the mosaic tiles is too uneven, those imperfections may start to cause the tiles themselves to look unevenly spaced. In wet areas like bathrooms, shower surrounds or kitchen backsplashes, use a backer board or waterproofing membrane.

Measure the area where you will be installing the mosaic tile. Using these measurements, dry lay the mosaic sheets to plan the layout, accounting for any cuts needed around outlets or edges. Mark your layout lines on the prepared surface using a level and straightedge. This plan will help you determine where to lay your first mosaic sheet as well as how the edge tiles will need to be cut.

For most tile sheets, you should be able to simply cut the mesh backing between the tiles. To cut the mesh backing, flip the tile sheet so the tiles are facing down and cut the mesh using a utility knife.

Using a level, mark a line on the wall where the bottom row of your tile backsplash will be. Then, using finishing nails, attach the ledger board to the wall using the line you marked to keep it level.

Mix the thinset mortar according to the manufacturer's instructions. Only mix as much as you will be able to use within about 20 minutes to prevent the adhesive from drying out before you are able to apply it.

Using the notched trowel's flat side, spread thinset mortar onto a small section of the prepared surface, following your layout lines. The grooves created by the trowel notches will help ensure proper tile adhesion. Work in small sections to prevent the adhesive from drying out.

Carefully determine the center of your tiling surface and mark it with a pencil or chalk. Press the first mosaic sheet and gently onto the thinset, aligning it with your layout marks. Gently tap the tile sheet with a grout float or a flat piece of wood to ensure even adhesion and to make sure the tiles are all sitting flat and even across the substrate. Use a level or a straight edge to ensure the tiles are even and aligned.

If your tiles aren't pre-spaced on a mesh sheet, use tile spacers to maintain even gaps. Periodically check the alignment and level of the tiles as you go.

Continuing to work in small sections, spread the thinset and apply additional mosaic sheets. Be careful to align the edges of the mosaic to maintain a seamless appearance between sheets. Leave a 1/8 inch expansion gap where the tile meets any other surfaces such as countertops or walls.

Allow the thinset to fully cure according to the manufacturer’s directions before grouting.

Using a clean bucket, prepare the grout following the manufacturer's directions. Aim for a consistency similar to peanut butter. Mix only as much as you will be able to use within 20 to 30 minutes to prevent the grout from drying out before you are able to use it.

If you are grouting mosaic tile on a wall, start from the bottom and work your way up. If you are grouting a mosaic tile floor, start at the point furthest from the door and work backwards.

Using the rubber grout float held at a 45-degree angle, work the grout across the mosaic diagonally, carefully filling the spaces between the tiles. Wipe away excess grout with a damp sponge. Keep a bucket of clean water on hand for rinsing the sponge and change out the water frequently to make sure it stays clean.

Allow the grout to dry for 15 to 30 minutes and then remove any excess grout using a grout shaper. Once you are finished, allow the grout to fully dry as specified by the manufacturer, which usually takes 24 to 72 hours.

After the grout completely dries, buff the tile surface with a clean, dry cloth to remove any grout haze. Once the tiles are clean, apply a grout sealer to protect the grout from stains and moisture.

After the manufacturer’s specified grout drying period, using a caulk gun, fill the expansion gap with caulk. This will add an extra layer of waterproofing and create a more finished, professional look.