The rest of the edging recall the motif used as a corner in the square: RW and start a ring. Rings are even the same 3-3-3-3-3-3, but you should be careful where they are joined to the square motif. First ring is joined after the first 3ds to the central picot of the chain in the square.
Then RW and start the chain. After 3ds, join it to the last picot of previous chain. Continue the chain.
Then reverse again work and start the second chain, like in the corner of the square. (Refer to pic 15.) That chain is joined to the outer ring, so for the chain : 3ds, join to the last picot of outer ring, 3ds, then repeat 1 picot, 3ds for 4 times.
Each pointed motif is repeated for the length of the collar. You should note that the connection point between squares is tatted the same as in the collar's corner, your left bottom side in the pic 18. BUT the chains are NOT JOINED.
When you reached the upper left corner of the collar, make a chain as usual, join to the central picot of the square's corner ring and tat another 3ds, join to last picot of previous chain and TAT ONLY 3 PICOTS MORE. That will take to the starting point of the edging.
You should be proud of your new collar. I'm not. It's unwearable. :(
Ok, let's start a real collar then!