See it happen...
Just a few brief points on the importance of falls, levels and dig-out for patio installation.
Before any work starts it is important to find out where any rainfall will go and any water lies, failure to address this at the start could result in a bad job before it has even begun. At the dig-out stage I will assess the suitability of the ground, if it is good why take too much out; if bad and particularly clay then at least 6″ or 150mm will come out. This dig-out will be more shallow than a drive as there will be only normal light foot traffic (no vehicles). I mentioned the importance of drainage from a patio, normally there will be no geo-textile membrane used on a patio as this is only used to prevent excess water from dis-placing any sand on which the patio is laid.
Once the dig-out is complete and the levels are in then I start the backfill with the required aggregates using Type 1 MOT/crusher run, this will be graded from 40mm to dust. I then use a full bed of washed sand and cement, generally mixed 5:1. Once the bed has been levelled then the laying of your patio will begin. I normally used one of three methods to point the flags; a pave-fix jointing compound, red sand and cement or a washed sand and cement mix, all depending on the type of flag laid.
The above is not a definitive method of laying a patio as every one is different but from all my years of experience it has stood me well and gained me an excellent reputation for standard of workmanship.