If you already have the patchbay, do it like this:
Insert sends to the top row of the patchbay on the back. Set the patchbay channels to be half-normalled. Connect the bottom row on the back of the patchbay to the insert returns. Take lines out from the top row on the front of the patchbay to the MOTU. Since its half-normalled, inserting lines into the top row on the front won't break the connection.
Insert sends to the top row of the patchbay on the back. Set the patchbay channels to be half-normalled. Connect the bottom row on the back of the patchbay to the insert returns. Take lines out from the top row on the front of the patchbay to the MOTU. Since its half-normalled, inserting lines into the top row on the front won't break the connection.