Mix together the olive oil, honey, mustard, salt, thyme, oregano and lemon juice in a large shallow container.
Pound the chicken breasts to uniform thickness and add them to the marinade. Cover and marinate in the fridge for at least 8 hours.
Heat a grill pan over medium-high heat. Grill the chicken in batches until golden brown on the first side, 4 to 5 minutes. Flip and cook until golden brown on the other side and cooked all the way through, another 4 to 5 minutes. Let the chicken cool.
Transfer the chicken to freezer bags individually and in pairs, so it's easy to defrost the exact amount you need.