Placing Cooking Surface (oven floor) on Hearth

[sledge]

Seeking a point of clarification here...I've got my hearth complete and I'm beginnning to layout the oven floor (cooking surface).

The Pompeii instructions say "Do not mortar the floor in place, but rather spread a thin layer of sand and fire clay to provide a slip plan between the oven and hearth. That will allow them to expand thermally at different rates. The underfloor is paste, the texture of a sticky mortar..."

They way I understand this is to layout a thin AND DRY layer of sand and fire clay. Then cover that dry layer with a WET layer of mortar (mixture of sand and fire clay and water). Is this correct? Seems that the dry layer would simply suck out the water from the mortar...but perhaps it doesn't take it all out I'm assuming a "thin" layer is about 1/4" to 3/16"...

Can anyone shed a bit more light on this by describing their technique? And would you do it differently if you could do it over?

Thanks,
Kevin

[paulages]

"dry" refers to a lack of cement in the mixture. mixing this wet will allow the sand/clay to be more workable, as you level each brick, yet will allow for everything to move independently once it dries out again.

spread the mortar out with your notched trowel, then use a rubber mallet to tap each brick level with the others. as the mixture dries out, it becomes harder to do this, as the mixture doesn't want to move around so easily.