In the Mixed Stitch Stripey Blanket Crochet Along, Little Woollie gives instructions for the Outlined Cluster Pattern:
One row of sc in red.
Next, one row of 4tr clusters in turquoise, made the same way as the 4dc clusters, but with trs instead.
Next row, ch1(counts as 1st st), 1sc in next stitch, then 2trtog into centre skipped st of the first row of sc in red, *then 3sc across top of cluster sts, then 2trtog into centre skipped st of first row of sc in red*, and repeat to end of row.
Do you need a visual?
I substituted pink for red, and purple for turquoise.... the first two rows are pretty self-explanatory, so lets focus on the third row, and specifically the repeating pattern instruction between the *. 3 sc across the top of the clusters - then 2trtog in the center stitch of the first pink row (the stitches that were skipped between the triple clusters). This picture shows which stitch you will work your 2trtog.
YO (yarn over) twice - so that you have 3 loops on the hook and insert your hook into the first row stitch.
YO and pull up a loop. You now have 4 loops on the hook.
YO, and draw through 2, leaving 3 on the hook.
YO, pull through 2 again, leaving 2 on the hook.
YO twice (4 loops on the hook) insert hook back into the same first row stitch.
YO and draw up a loop - but instead of 4 you have 5 loops on your hook.
YO and pull through 2 (leaving 4 on the hook) and again YO, pull through 2.
You now have 3 loops on the hook and are ready to close the stitch.
YO and pull through all 3 loops.
3 Sc across the top of the next triple cluster.