If it was still uncured then Acetone or White Vinegar. Since by now I assume it's cured then I would just carve it off with a sharp exacto or it should come free pretty easily from covering if you have it stuck to that. Of course a huge puddle of epoxy seems rather wasteful. Built me a canoe using epoxy... try mixing and pouring 3 to 6 ounce batches on a regular basis, 6oz makes a large puddle!!!