Instead of cutting biscuit slots into the edges of frame parts, use a biscuit joiner to cut a pair of them into the back face across each joint.
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While making a face frame for a bathroom base cabinet recently, I decided that mortise-and-tenon joints were overkill, and half laps were too time-consuming. I wanted to use my biscuit joiner, but the face frame was too narrow to accept standard-size biscuits. Instead of cutting biscuit slots into the edges of the frame parts, as I normally would, I cut a pair of them into the back face across each joint (as shown at right). After gluing the biscuits in place and letting the glue dry, I cut off the protruding half of the biscuits with a handsaw. (They won't be seen inside the cabinet anyway.) You wouldn't want to use this method for joints that will be under a lot of stress, to be sure. Nor would you use it where the back of the frame will be visible. But for face frames, the joint produced is quick, easy, square, and plenty strong.

-Len Estrada, Gladstone, Va