Control temperature with microwaves and use ultrasound to control crystallization
Microwaves can in principle change temperature from inside of a body, and ultrasound has been shown to be able to "control the rate of crystal growth, ensuring small and even-sized crystals are formed, and can prevent fouling of surfaces by the newly formed crystals" (link).
A simple idea would be to combine the two, in order to slowly traverse the crystallization barrier with minimal damage, but I didn't find any attempts to that.
While you can reduce the ambient temperature very slowly without microwaves, introducing microwaves in low powered randomized pattern unfreeze at random locations, and maybe let some of the tensions within ice to even-out before they result in fractures.
I would look forward to experiments of freezing at least a glass of water with different microwave and ultrasound patterns to see if you can control where the fractures occur, and how uniformly it freezes using these means... and maybe you would want not just ultrasound, but sound with more diverse wavelengths.