Joining Mandalas

I have so many mandalas, it's ridiculous, and there isn't much I can do with them. So I've been trying to think of how to make them square. Then someone I follow in Instagram was making a beautiful blanket with hexagons (@dreamsofanne), and I thought it would be easier to turn circles into hexagons than into squares. So I thought about that off and on for a while, but I wanted rectangular edges which is hard with hexagons. I know this from quilting. Then two days ago I had to clear off the sofa in the sewing room where the mandalas are piled. I must have dreamed the solution because the next day I came up with this idea and it works. Make the mandalas into octagons and then pick up stitches on the diagonal edges and reduce at the corners each side by working 3 dc together.

The mandalas are all the simple mandala by Wink (link here). To make the mandala into an octagon start at 4th dc of any 6 dc scallop (US terms). Over each set of three scallops work: * sc, 2 hdc, dc in sc between scallops, 2 hdc, 2 sc, one hdc, dc, then work 8 tr over next sc-scallop-sc, dc, hdc, sc. Repeat from *. Invisible join.

To make diamonds, work from large diamond to small, 5 rounds.
For the first dc 3 together, you have to ch 3 for the first dc.
For the center diamonds, the first 4 rounds should be joined with a sl st. Work in ends before starting the next round. I find invisible join to be too complicated here. I also vary the starting edge so that I'm not joining each round in the same corner.

(round 1) start in 5th of 8 trs on each octagon side: dc 3 together, dc 15, dc 3 together along 1, 2 or 4 sides depending on whether you're working the corner, side, or a diamond in the middle. End in 4th of 8 trs.
(round 2) start in first dc together: dc 3 together, dc 11, dc 3 together on each side.
(round 3) start in first dc together: dc 3 tog, dc 7, dc 3 tog on each side.
(round 4) start in first dc together: dc 3 tog, dc 3, dc 3 tog on each side.
(round 5) dc all remaining stitches together. if working the center diamond you will have to use two hooks, and when pulling the final loop through you will have to transfer the loop from one hook to the other. Be careful not to drop the loop on this step—it's hard to recover. Pull loop through and secure on the back.

My mandalas are two sizes because I used an "H" hook for the ones in the picture but an "I" hook for a few others. So my plan is to make a center, add a border to widen, and then add the larger mandalas to the sides. We shall see, this project is not my #1 priority and I don't have enough mandalas to finish a complete blanket.

I apologize for any ambiguity or errors in the instructions.

Whoops I forgot to mention, you have to join the octagons together. I used zipper stitch - sl st through back of loops of both sides together. I'm sure other methods would work too. I'm not done designing so I'm not sure if it makes sense to join into the first and last stitch of the diamonds so as to not leave a gap.