DIY multi-purpose Garden bed Box
Step 1. Cut the boards and mark the trenches
From 1x6 boards, cut 24 @ 4ft long.
Clamp them together with the ends flush, and mark a line across the boards at each end, positioned as follows:
# Make the lines approximately 4" in from each end.
# Ensure the lines are exactly 40" apart.
Mark another couple of lines across the boards, one at each end, in 1-1/16" from the first lines.
The area between the two lines at each end is the slot cut-out area. The width of the cut-out area should be slightly wider than the width of a board, i.e., a board (in this case) is 1" thick. Therefore make the cut-out area 1-1/16".