Using DK (Double Knit) yarn and a 4mm Crochet hook, make a sliding loop and pop in your hook before tightening (do not pull too tight or you will find it hard to get a stitch into it later on)
So, break of your colour and pull it through the last stitch to secure, then loop the new colour inbetween two TC's.
Slip stitch into the top of the original 3 chain at the start of the row to join,
then slip across the next two stitches so you are at the corner ready to begin a new row/round.
This is your four corners in place.
Let's change colour again to make things easier.
So, 3 chain, then 2 x TC's, 2 chain, 3 x TC's in first space.
Jump to space in the middle as shown on photo.
Do 3 x TC's (no chain or extra TC's, just the three)
Jump to the next corner and as you are working a corner, do 3 x TC's / 2 CH / 3 x TC's into that space.
Continue in the manner until the row is complete, and slip across the top of the first cluster to arrive back in a corner space for the next row.
Basically just continue, always remembering to work the corners with two lots of 3 x TC's with 2 CH and just the 3 x TC's on the straight parts.
You can carry on making it larger and larger, or make a collection of smaller ones and fix them together :)
If you prefer to print these instructions you can find them here: www.soozintheshed.co.uk/grannysquare.pdf