When I did my granite countertops, I used the cut-out from the sink to get two window sills to match. However, with the size you mentioned, I can't think of any other use than the one everybody suggested (slab for pastries/dough/candy)
Can the fabricator cut it thin (like tile), if you get 4 of those, you can use them for the top surface of a kitchen cart to match your countertops. This will require a bit of work, I am not sure how much expertise you have.
"Tell me what you eat, and I will tell you what you are" Anthelme Brillat-Savarin