Foundation for Casa110 modular oven

[jbuildarkansas]

I'm about to get start installing a Casa110 on my back patio. The patio is constructed of large slabs of rock and around the periphery is brick. I want to place the oven at a corner of the patio so that the front half would be over the existing patio and the back half would extend out into the yard.

My question is, do I need to remove the portion of the patio on which the oven will sit and make one slab or can I just pour an extension slab to accomodate the back half of the oven?