Start by planing a board down to 24 × 38 mm. Then cut the pieces to the lengths shown in the drawing, making two strips for each side.
Next, cut the rebates using a table saw or router, depending on the tools you have available. On two of the strips, 38 mm of the rebate must be removed at the ends as shown in the drawing so that the parts fit together correctly.
Once the strips are prepared, assemble them using glue on the contact surfaces together with nails or screws. Make sure the frame is perfectly square before the glue sets.
Then cut a sheet of 4 mm plywood to the dimensions specified in the drawing. A hole should be drilled or cut in the centre for a bee escape. Even if a hole diameter is shown in the drawing, it should be adjusted to match the type of bee escape you use.
Fit the plywood panel into the rebate and fasten it with nails or small screws.
Since the panel is protected by the outer roof and is also in direct contact with the bees, it should not be painted or treated on the inside.