The longer you wait, the more damage you cause to the cells since they’re not meant to be in that state. So try to get them charging as soon as possible.
Check individual cell voltages!!!
This is the most important thing you need to do. You need to verify that all the cells are above 1V. If any of them is below 1V, do not charge the battery. This is explicitly stated in the datasheet of the cells. Charging a battery under 1V has a high risk of fire.
Keep the cells cold. Between 5C and 15C ideally. Between 0C and 20C is ok. Charge cells slow. 0.5A per cell or lower. (2A or less for a 4P) Keep an eye on temperature when charging. Anything above 35C and you should let the cells rest before continuing. Do not use a BMS when recovering cells from under 2.5V. Check voltages constantly with a multimeter, making sure they are charging evenly. Charge to at least 3.6V before connecting BMS. Charge outside on concrete surface in case of fire. After you charge to 3.6V let battery sit for an hour or two at room temperature. Plug in BMS and charge normally to 4.2V. Check that cells are balanced to 50mV at worst.
If you do not follow all of these steps exactly how I wrote them, you are risking your battery and surroundings to a very serious fire.
VTC6s are some of the most resilient cells out there but you must be extremely careful still.