In Mississippi your Will does not have to be notarized. It has to be executed by you in front of two witnesses who sign to witness the Will. You have to be in the presence of both witnesses at the same time you sign and they sign.
A self proving affidavit signed by the witnesses does have to be notarized. It is used in order for the Will to be probated and prove the witness signatures and is often signed at the time of making the Will.
It is common to use the self proving affidavit at the time the Will is made.