This is how I prep for Cuban style pork roast.
I make a paste of garlic, salt and freshly toasted and ground cumin seed. For the roast, I use a pairing knife to open deep pockets all over it. I rub the paste all over the roast making sure to pack it down the pockets. Be very generous.
Using a mandolin, thinly slice two large sweet onions and place them inside a two gallon zip-lok bag laid on its side to form a bed. The bag should be in a baking dish or aluminum pan. Place the roast on top of the onions. Next I pour fresh squeezed sour orange juice (2 to 3 cups) over the roast and seal the bag. Marinate over night in the fridge, turning several times. If you can't find sour oranges, use 1/2 & 1/2 orange and lime juice. Remove roast from marinade and pat dry. Reserve the marinade. I've cooked these roasts in the Egg, both hot and fast and low and slow, using lump only.
For the reserved marinade, thinly slice as many cloves of garlic as you wish and add to marinade. I like it really garliky so I use a whole head. In a deep sided frying pan, heat 1-1/2 cups pure Spanish olive oil, over medium high until shimmering. Next step requires extreme caution. Remove pan from heat and pour the reserved marinade into the oil. Once things have settled down, return to heat and simmer until garlic and onions are soft. Serve either warm or at room temp. It will be good over the meat or on a side of yucca. Black beans, rice, maduros or tostones and Pan Cubano round out your guests err I mean meal.
