Disposal-dishwasher wiring clarification

[reader4]

Just talked to my inspector who reminded me about fixing my disposal/dishwasher circuit. We talked about using the same circuit for each but he mentioned something about including a switch below the sink that I am confused about... here is what I am thinking...

Run 12/3 to a 2 gang box.
One hot goes out to the switch leg and comes back for the disposal.
The other hot connects to a 2-pole switch in the box to power the DW.

I think this is what he was talking about, but can anyone clarify/corroborate? He said this sort of hookup is pretty common.

[HayZee518]

bring your power up into the cabinet under the sink to a handy box or a four inch square box with a single switch raised cover. neutrals are spliced together. hot goes to the switch - return goes to the disposal - black to black, white to white, green to ground screw or green wire. A batch feed disposal has a magnetic switch in the plug. with water flowing the unit turns on when the plug in the drain is inserted. the switch under the sink is a safety device to turn on the disposal.