Measure the width of the window you have selected as the location for your window stool project using a tape measure. Measure from the outside edges of the window casing to get the full span of the window’s width. This measurement is the length dimension that is required for the seat.
Place a 2-by-16-by-96-inch board flat on the table of a miter saw. Use a tape measure and pencil to measure and mark the board to the measurement that you took in Step 1.
Slide the board along the table of the saw until the pencil mark lines up with the outside edge of the blade. Saw the board to length with the miter saw.
Sand the cut board lightly with a fine-grit sanding block until it is completely smooth. This is the seat board for the stool. Wipe off the sanding dust with a tack cloth.
Spray a coat of lacquer onto the stool seat and allow it to dry for at least four hours. Apply a second coat. Wait 24 hours after the second coat before continuing with the project.
Lay the seat board flat on a work surface with the bottom side facing up. Center a stool leg in each corner of the seat board. The outside edges of the legs should be in 3 inches from each outside edge of the seat.
Drive the screws that were included with the stool legs into the board to fasten each leg in place using a screw gun. When selecting stool legs, choose legs that will make the stool seat at approximately the same height as the window sill for an aesthetically appealing arrangement. Turn the stool upright and place it in the window.