Check the brick slips before installing. The substrate should be clean, workable, solid and even. Apply a suitable adhesive with a toothed spatula. Float the brick slips firmly into the adhesive. A string line will be helpful.
Always mix the brick slips from several boxes. Smooth out the adhesive in the joints with a wet paintbrush. If you wish a joint filling, after 24 hours, use a pointing mortar for bricks. Apply it with a traditional metal trowel. Do not plaster the joints with a tile grout.
For all brick slips there are suitable corners. Brick slip corners may vary slightly in appearance due to production.