My favorite sideswiper CW key, made of a hacksaw blade. The smaller pieces of wood can be moved to adjust the tension. The clamp holds them steady between the larger pieces of wood (which are attached to the base).
Wood screws act as contacts. The fingerpiece consists of a coin under layers of electric tape.
Wires are connected with alligator clips.
The key needs to be clamped to the table...
... or better: mounted permanently under the table with screws.
In my experience it is much easier to send good sideswiper code without resting the hand on the table. The whole arm moves, not just fingers: