Do them on the table with the fence attached. Clamp them together, with short sacraficial pieces on each side, and use the fence to set the edge of the groove closest to the end, then back the fence away from the bit if you need a groove wider than the bit. The sacraficial pieces will give you clean edges and help counterbalalnce the overhung end. You can support the overhung end with one hand and use the other to push them over the bit. Take off 1/4 max in one pass. You could probably eyeball the boards to get a square cut (i.e. keep them perpendicular to the fence) but it might be easier with a miter gage.
“The single biggest problem in communication is the illusion that it has taken place.”
George Bernard Shaw
Redondo Beach, CA