You must appoint certain roles
Your board of trustees must appoint a senior executive leader for the trust. This should be the chief executive or equivalent and they may also be appointed as a trustee.
This leader should also be appointed as your accounting officer, another required role, where they'll oversee financial transactions.
Additionally, your board must appoint a chief financial officer (CFO). They'll be responsible for your trust’s detailed financial procedures, and they should play both a technical and leadership role.
Both of these individuals should be employees of your trust.
See sections 1.33 to 1.48 of the Academy Trust Handbook (ATH).
Overall structure is up to you
There are no other specific rules for the leadership structure of trusts.
Your structure should be appropriate to your context and central team capacity. You should also make sure that the structure allows stronger school(s) in your trust to support the improvement of weaker schools.