I know everyone hates packing peanuts , but I add them to the bottom of my pots and have very good luck.
Here it is the water expanding when freezing that cracks the pots , peanuts flex and relieve the pressure before the pot breaks.
I have over 50 pots that stay out over winter .
The other suggestion is elevate them from the ground, the ones that sit on the ground often crack on the bottom due to outside pressure.
