This pattern gives a pretty variation on the standard garter stitch mitred square by placing a stocking stitch heart in the centre of the square.
In a variegated yarn the heart gives a subtle touch, but in a plain yarn it makes a bit more of a feature.

Yarn, needles and gauge are not specified as this pattern is intended to be a variation on any mitred garter stitch square - just divide any extra stitches evenly between the garter stitch areas around the heart and it will fit within your favourite pattern.
However, the pattern instructions will give a 5-inch (illustrated), or a 6-inch square, when knitted in a DK yarn on 4.5mm needles with 6 stitches to the inch/25mm over stocking stitch.