Heat a large pot over medium heat. Add in the olive oil and cook the carrots, celery and onion with just a pinch of salt until they begin to soften, about 5 minutes. Add in the garlic, cooking until fragrant for another minute, then add in the chicken stock and ham hocks. Strain the beans from the water and add to the soup. Do not add in any more salt since the beans absorb the salt and can get too salty. Season with salt at the end of cooking.