Here are the details, step-by-step, so you can also make your heart-shaped placemat for two, in crochet.

MATERIALS
t-shirt yarn
crochet hook (indicated for the t-shirt yarn you have – I used a 10 mm crochet hook /USA: N /UK: 000)

TECHNIQUES THAT NEED TO KNOW
chain
slip stitch
USA – single crochet (sc) | UK – double crochet (dc)
USA – double treble crochet (dtr) | UK – triple treble crochet (trtr)

AFTER CARE
Wash your piece in a bowl with cold water, or warm, and a little soap to wash clothes by hand.
After washing, spread it on a towel and wrap it with it (the towel will absorb most of the water).
Finally, let it dry on a flat surface (to prevent that deforms).