Mortar mix for concrete counter top under oven?

I am making concrete countertop with the center cutout for the firebrick center, which will be set on top of the base.

Do you recommend putting the high-temp mortar mix under this countertop or would regular mortar mix be ok?

Regular 'ol mortar mix will be fine!

Sounds like a cool base! When you are all finished, please be sure to send photos of your oven project to:

Thx!

Here you go -