Add the whole piece of meat, prepped and ready to be cooked and then add more cocacola until it covers the meat, use some of the vegetables to cover the meat so the meat is completely submerged in the marinade.
In the pot that you are going to slow cook the meat, cover the bottom with oil and sear the meat until charred all over. (Make sure to open windows and prepare yourself for a LOT of smoke)
Take out the meat and let it rest, meanwhile blend the sauce and season with salt and pepper if needed. Once it has cooled, slice the meat into 2-3 cm thick pieces and put them back into the sauce, and let it simmer on low for 30 more minutes.