I'll show you how to make pin tucks after the cut.
I measured the duvet cover and decided to place my pin tucks 10 inches apart. I made a template 10 inches square and drew intersecting lines at the five inch mark on each side.
I turned the duvet cover inside out, laid it out flat and then using the template as a guide, I made a mark every 10 inches using a washable pencil.
For the second row, stagger the marks, starting off with the first mark 5 inches in from the one on the previous row. For the third row, start off your mark in the same position as you did in the first row. Alternate placement for each following row.
Your grid marks should look like this:
Grasp the fabric where it is marked with your finger tips and then twist the end.
Stitch back and forth a quarter of an inch from the end a few times.
And that's it. Simple.