This is a simple technique using filet crochet. The diagonal pattern is reversed after several rows and doubled so that 2 diagonals are created to every one previously. As the pattern doubles back on itself a 3rd diagonal is added to the set. A halfway point is noted in the pattern but you could make it bigger or smaller once you’ve grasped the principles of the pattern.

It is a bottom up pattern so can be made to any size desired. Although the pattern looks complicated it isn’t really once you have grasped the principles of moving the ch1 gap along on each row. I have made this in Mandala, but an earlier version in a plain block colour looks better because the pattern stands out more.

This is not a professional pattern, just an enthusiastic grandma who likes to create.