How to make a Hall Bench or Bed End Bench.

Instructions continued (steps 8 to 9)

Step 8. Seat support strips

From 32mm x 20mm (3/4″ x 1 1/4″)stock, cut two pieces to length to fit between the two end rails.

Screw them to the front and back rails 22mm (7/8″) down from the top.
That is slightly more than the thickness of the seat boardA piece of sawn, or dressed lumber of greater width than thickness. Usually 19mm (3/4") to 38mm (1 1/2") thick and 75mm (3") or more wide..

The seat support strips are solely to support the drop-in seat.

Step 9. A bit of paint

We used high gloss enamel paint and applied three coats over three days giving a slight sand before each new coat.

You might want to do something different, such as stain and polyurethane.

It all comes down to what sort of finish you want and what sort of woodTimber, lumber. The hard fibrous lignified substance under the bark of trees you use.