A reinforced mortar-bed substrate is key to success
The setup involved establishing a level perimeter with 2x4s, straightedges and clamps.
Three-quarter-inch OSB formd the edge of the top.
I relied on my eyes and a marker to get a profile that would complement the rocks immediately below the top, and used a jigsaw to make the cuts.
I bent 9-gauge (1/8-inch-diameter) stainless steel rod to reinforce the undulating edge of the mortar bed, placing it about an inch in from the perimeter and following the shape outlined by the marker.
Once the perimeter rods were shaped and bound together with stainless steel tie wire, I removed that assembly from the top while I worked on the perimeter screed. For this, I used a paper and metal drywall corner bead, snipping it so it would conform to the curve of the top.
Each 8-foot section of bead was fitted.
I secured the screed with screws.
