Standard showers and bathrooms are encased with ceramic tiles or natural stone tiles. Do note that granite slab installation is a professional job. It is not recommended that amateurs should handle such projects. You have to explain what you want to the installer as different people have different perceptions of beauty.
To start, measure for any kind of cutouts needed for the shower's action wall. This wall can be identified by the shower head and hot/normal water spouts. Use the tape measure to find out where there is a requirement to cut holes within the slab. This will make the pipe cut-outs. Mark granite, and use drill. This will cut out holes.
It is important that you first install back slab first prior to installing two side pieces. Do mix the epoxy glue and then spread the same to the slab piece's back. It is important that you have a working partner or multiple working partners if you face heavy slabs. Maneuver slab into its desired position. Position it firmly on the existing backerboard or concrete board already present in the walls.
Slab and epoxy
Firm pressure is applied and move slab up and then down. Move them also from one side to another side so that the epoxy glue binds them firmly to the wall behind them. When finished, permit slab to go the final resting place. This will be on the top of the shower pan. Repeat this process for two side slabs. Put the epoxy glue in horizontal gap between the slabs which need to be stacked on the top of one another. Allow weight of the pieces themselves to press together. Once done, scrape off excess epoxy. You can do this by using a plastic putty knife. Use an acetone dipped towel to remove epoxy haze from the slab face.
Cover the wood pieces ends with the towels. Use them to put back slab against shower pan floor. Brace side walls against one another. Keep braces like this for a minimum of 24 hours. Follow the manufacturer's instructions in case of any doubt. After these are done, remove braces. Apply the silicone caulking to inside corners. Fill gaps between slabs. Do silicone areas where slabs meet shower pan. The caulking must be dry for a minimum of 72 hours prior to using that shower.
Here are a few words of caution: measure as many times as possible but cut only once. If you miscalculate, the slab will be ruined, leading to financial loss.