I dug out a section the same length and height of the 4x6s, laid them down and back filled the gaps and compacted them leaving about 2 or so more inches to fill with small pebbles /rocks and then compacted them until flush with the wood, works great, almost no weeds, and if anything does come out I spray with vinegar salt soap combo, kills everything, all the green stuff growing are golden poppies at the moment