Cannot figure out how to install rubber ring which is below sink ring and above motor unit. Grooves seem not to be BOTH accessible. upper lip on rubber ring can go into collar attached to sink. But lower lip cannot be inserted into groove before attaching hold down (metal) clamp which secures the motor (lower) unit to the sink ring and collar unit. Need 1, 2, 3 instructions on the ORDER in which rubber ring and metal attaching ring are to be put in place for initial installation of Waste King 2600.