In most circumstances, a Stock Assignment form or a Stock Transfer form is required to assign rights to company stock in an estate to a beneficiary of that estate.
This document could or should be prepared by the Executor of the estate — not left up to a beneficiary to create.
Further, the Probate Court where the probate case has been filed may need to approve the stock transfer in advance (approval typically is not required of individual family members of the Maker).
To easily create a valid Last Will and Testament that transfers company stock to a beneficiary (named or otherwise), see Standard Legal’s Last Will and Testament legal forms software page.