Fresh basil for instance can not be substituted for fresh.
Simply pick fresh good leaves from stalk place on baking tin and place in freezer. They will freeze quickly due to size of course, remove and place in a airtight container in the freezer for further use.
Try and remove desired basil leaves as quick as possible from the freezer since they defrost very quickly and you don't want the remaining ones in the freezer to deteriorate.
I the frozen basil leaves in the last stages of cooking, in sauces, casseroles, risotto, pilaf, into flavoured breads such a basil and olive focaccia, salad dressings and much more.