Finish With Trim
Dry fit the window bench in place (Image 1). Create a plan to "trim out" the bench. The Blog Cabin 2011 window bench was finished with beadboard, corner trim, a baseboard and edge trim.
Pull out the bench and lay it on its back. To cover the two sides and the front of the bench with 1/4" x 4" t&g beadboard, cut each piece to fit vertically from the base of the bench to underneath the top seat overhang. Glue beadboard in place before nailing (Image 2).
Measure and cut baseboard to length, taking care to bevel cut the corners for a corner tight joint. It is better to cut long and dry fit, trimming as needed.
Measure two vertical corner trim pieces and cut to cover the front corners where the beadboard panels meet. Set pieces on top of the baseboard and snug them up under the seat overhang (Image 5). If accessible, use a brad nail gun or micro pin nail gun to secure the corner trim in place.
To cover veneer cross bands on the bench seat, cut a 3/4" edge trim to fit and micro pin nail in place. Note: Measure and cut the corner bevel for a tight joint. Glue the edge trim before nailing (Image 6).
If accessible, use a brad nail gun to minimize end splitting and to reduce the nail hole size. Attach the beadboard with at least two brad nails at the top and two at the bottom (18 ga. x 1 1/4").
With the bench on its back, use a speed square to align the bottom of the baseboard and corners (Image 3). If accessible, use a finish nail gun or brad nail gun to secure the baseboard in place (Image 4).