Easy
This pattern is written in US Crochet Terminology and uses standard Crochet Abbreviations.
Repeat row 4 (increasing the number of side 3dc clusters on each row) until the desired size.
Some granny square patterns have a ch1 in between each 3dc cluster. I don’t like to do this, preferring the more sturdy square produced when the ch1 is omitted. However if I’m going to ‘join as I go’, I’ll then add a ch1 between each cluster on the last row only.
Also, if your plan is to make your granny square any bigger than 4/5 rounds I strongly suggest that you turn your work after each round working alternate rounds on the front and then the back. This will help to keep your work square.