Several months can pass from the signing of a contract until the new employee starts. Preboarding is what the company does during that period. The goal is for the new hire to feel welcome and not have second thoughts.
Typical preboarding includes a welcome email, a plan for the first day, practical information, and the name of a contact person. Some companies also give access to a short intro course about the company, so the first day can be spent on people instead of presentations.
Keep preboarding light. It is not working hours yet, so the content should be voluntary and short.