The idea surely isn't to melt the wax to release the honey, but to warm the honey so that it leaves the wax, which hopefully will melt after the honey has drained.
The tray will be hot enough to melt the wax, but the honey should rapidly leave the wax and be in the wax separator before it has reached any significant temperature.
There is a design for an uncapping tray shown in "Honey By The Tonne", Oliver Field, but it would be difficult or expensive to approximate the surface.
The Apimelter has a fan blown grill type elements above the wax and a gentle heater below to facilitate the release of the honey. The wax provides a thermal barrier over the honey which should largely have been recovered by the time the wax is ready to flow.
This would be facilitated by an open, loose mix of honey and cappings and not overloading the melter so that it is able to drain away into a cooler environment relatively quickly. So steep angles and lots of opportunity to drain are probably the order of the day.
As Itma says, melted properly, not necessarily completely or in the same instantaneous time frame.