MD that's correct. incoming OWB water is on the bottom, outgoing indoor boiler water from the plate is also on the bottom. Hottest water is in contact with hottest water. Perfect.
fireboss- that'll depend on the boiler. Every boiler has a direction of flow. The Weil McLain like MD has pictured is designed to return to the bottom (pump side) and supply from the top. Whatever you have should be labeled supply and return on the boiler, but if it's not, if you can get me the make and model number I'll find the correct piping direction for you