Flaked Rye in Kvass

We are going to brew a Kvass and all our LHBS has is flaked rye. Is it fermentable?

To make a kvass, you should bake some rye bread. Soak the bread in some water. I don’t know if the Russians pitch yeast, or just let the natural ferment take over. I will ask some Russian friends and repost. I know they have made it before.