Cob bench with brick

I'm planning to make a cob bench under a protected porch.  I have some clay soil, but just acquired a whole mess of used bricks.  Does anyone know if it would it be possible to make the bench with mostly brick and then do a top coat with cob to found it out and at some artistic elements?  If so, should I use an earthen mortar between each brick or do you think I could dry stack a layer and then put a layer of cob mortar across the whole layer and keep repeating?  Since its protected and doesn't get much moisture would it still be good to put a layer of pea gravel in the bottom for drainage?  Any suggestions or advice would be much appreciated.

Oh, and its being built on a concrete slab