Can you increase friction on the edge of the puck but not its bases? That should make it tip over.
I created a physics material for the puck, and that's where you set the static and dynamic friction properties. There is something called anistropic friction, where you can set a friction direction. I suppose that means you're setting an axis that has a different friction value than the rest? Edit: I looked it up, and it's definitely controlling friction along x,y,z axis, but I don't know if that's relative to the object's local axis or the world/global axis.
I also realized the primitive cylinder they provide has a physics collidor (hitbox for physics detection, basically) in the shape of a capsule, so it had rounded sides. I changed it to a mesh based collidor so it could lie flat, but it still tends to wobble on its edge and not fall.