Assuming the patio slabs are concrete, there is is a damp proof membrane under the slabs, they are bare, clean, dry, sound and prepared as detailed in the technical data sheet we can recommend the system below.

 The bare concrete must be acid etched prior to application.

Coo-Var Acid Etch

Followed by 3 coats of Coo-Var Anti-Slip Acrylic Floor Paint with the first coat thinned 10% with clean water.