Gary I used to use a 3D printer bed heater with a thermostat connected to my BMS. Since your LIOn’s have a built-in BMS I would look at any of the over the counter self-consumption heating wraps/blankets.
https://lionenergy.com/products/battery-warmer
Other manufacturers offer similar at varying prices. Google is your friend.
PS bet you could snag another Q deal on them too