Mo. Rev. Stat. § 115.300: Preparation of absentee ballot envelopes, when, by whom.

In each jurisdiction, the election authority may start, not earlier than the fifth day prior to the election, the preparation of absentee ballots for tabulation on the election day. The election authority shall give notice to the county chairman of each major political party forty-eight hours prior to beginning preparation of absentee ballot envelopes. Absentee ballot preparation shall be completed by teams of election authority employees or teams of election judges, with each team consisting of one member from each major political party.