open any old item as an Enchanted Device, but you must open it personally (no other can open a Talisman for you)
take the now opened device, and spend a season attuning it as your Talisman
step (1) is limited by your current MT2, Size and Material of item
step (2) lets you re-open the Talisman using your Art scores as the limit, but still no more than 2MT in any one season.
See TMRE Talisman chapter for more info, and more things to do with a Talisman.
I don't see the problem. The amount of vis the can be used to open an item for enchantment, including one intended to be your talisman, does depend solely on the size and material. The arts of the creator only limit further opening of a talisman, not the initial preparation of the item that will become a talisman.