In the contract creator, a master service agreement can describe the first engagement itself. Answer what services will be performed, in plain language, and that answer becomes the services clause. You also set the fee and how often it is invoiced. You can start from that agreement without writing a separate statement of work.
If more projects will follow, say so. The agreement then keeps room for a statement of work or an order form for that later work, and the legal terms in the master agreement still apply. You can also leave the first engagement out of the agreement and attach every project the way you did before.
