The divider is only 2 slats of wood wide. That is 3.5" x 2 = 7" but the soil only comes upto the mid point between the 2 slats.
Example: You have a fresh grassy ground un-dug border in front of you.
+ With a sharpened border spade (spade width only) you scoop a 2" layer of turf off 1.2m in length. Leave turf in pile to dry as we want the good quality top soil for our new bed.
+ Then dig the 2 small holes 4" deep for the legs of the bed divider. Position divider in the holes.
+ Using you spade scoop off turf, 1.2m x 75-80cm
+ Dig a small v shaped trench in front of the divider piling this soil on bare soil, it will get dug in during next step.
+ Now start digging 2" slither cuts full depth of spade in bared soil nearest the divider. With a quick deflection of the spade heap the slither of soil against the divider. This is a very easy way to dig over old compacted soil.
+ Water this dug section and leave a few days for water to saturate.
+ On return a light dig over then riddle top couple of inches. keeping large conker sized stones for filling divider.
+ Shake out soil onto your new bed from the dried turf pile. Waste grass onto your compost heap.
+ Finally shape this light fluffy soil border. Dip at back rising to a slight mound with long slopeing section.
NB1: Only fill about 2" worth of large conker sized stones. The larger the air gaps between the stones the dryer the stones will be. Slugs do not like warm & dry stones.
NB2: As a final stage I edge my new border with a woodchip filled mesh plastic baffle.
Yes normal untreated pallet (most are untreated i've been told)
It is just a different bedding technique, that recycles an old pallet (free) instead of expensive timber and makes use of the waste stones from your soil. Yes there is an initial level of faff to start with but going forward into your 2nd growing season it will all be a lot easier. It saves water & time, stops a soil crust forming and I have less plant failures and better yields.
It probably does suit you larger more water greedy plants such as Courgettes, Marrow, Squashes, Cucumbers, Sunflowers, Sweetcorn and potatoes.