I thought you might like to see how the squares are made for these cushions.
The colourful squares below are the traditional Granny Square, although I've changed the border of one (2nd from right at top in the photo). The plain squares are just one stitch: Double Crochet (UK) or Single Crochet (US) worked in rows rather that a round.
TOP RIGHT: I crocheted two rows of Double Crochet (UK) or Single Crochet (USA), one blue and the other white. As you can see, it gives a very firm edge as well as a bit of a different look but without changing the size or shape.
UK instructions are on this blog post by Little Tin Bird.
US instructions are on this blog post by Fibre Flux.
Here's my blog post for my huge Granny Square cushions, if you'd like to see them.
Simple and straightforward Double Crochet (UK) or Single Crochet (US).
Crochet terms are different in the UK and USA, so I've given links for the squares in both UK and US terminology, so you can follow the tutorial that best suits you. Here's a good post by About Home, which explains the difference and gives you both sets of terminology.