Any necessary adjustment units shall be placed on and interleaved with bedding mortar and tamped to the required level leaving room for the top layer of mortar.
Lay a top layer of mortar about 50mm wider than the frame in one even pass. If this is not achievable, then wedges should be used, and mortar packed under and around the frame by hand.
The final mortar course for setting the frame should be all one mix.
The finished sandwich of adjustment units and mortar with the frame on top can be tamped, but not the units themselves (as they will 'spring').