So I first made 3 times 4 granny squares which went really fast with this bulky yarn and a 6 mm hook.
And crocheted together and with a double crochet border at the opening those squares became comfy slippers.
You can find the instructions for assembling here. By the way I already made two pairs before and gave them away. This pair is for my brother. I will add a (liquid) dot rubber sole (Is there a special name for it?).