Patio onto a concrete base

Hello,

Looking at laying a patio onto a concrete base - pic attached. Will be using 600mm x 600mm x 20mm Porcelain slabs.
Whats the best method to lay these? Do we apply a 30mm mortar mix, then lay directly on top?

Also we would need to cut a small section for the down pipe drainage area, is this ok to cut with a handheld angle grinder?

Thanks
Matt