Here's my Sharpie tie dye fat quarter. I auditioned it with other fabric and found a pretty intense aqua that worked.
I cut four 9" squares from each and used the instructions for "Peppermint Pinwheel" in Cultural Fusion Quilts to make two blocks.
The pieces are kind of wonky when the sewing is complete. I pressed each piece well and squared to 7". Then I made two blocks.
I'm probably going to put them together the same way I used two blocks made with a leaf print fat quarter back in 2015.