Today's square is very similar to the one completed on day 7, I've made a couple of tweaks to the pattern which I think have improved it - there is no obvious join on each round for instance:
Start with a ring of 5 chains joined with a slip stitch.
5 chains, 3 treble crochets, *2 chains, 3 treble crochets, repeat from * 2 times, 2 chains, 2 treble crochets, finish round with a slip stitch in the initial 5 chains of this round.
5 chains, 2 treble crochets in chain space from previous round, treble crochet in each stitch from previous round - working through both loops in each stitch. When you reach a corner do 2 treble crochets, 2 chains, 2 treble crochets in the corner space - except on the final corner where only 1 treble crochet is worked. At the end of the round join with a slip stitch in the initial 5 chains of this round.
Repeat this as many times as necessary to get the size you want. I did the final round of treble crochets and then a round of double crochets in a different colour (mainly because I am using up the end of balls of wool, but also to add contrast!).