Building ships directly into reserve

Can a navy build ships even when it cannot immediately crew all of them?

Yes. Navies have placed new ships directly into reserve, preserving them as replacements or surge capacity while later members of the class remain active.

Direct-to-reserve construction can preserve ships for later use. In a class of twelve, for example, the first four might enter reserve immediately or once the later ships have entered service. That gives time to correct early design choices and upgrade the first ships to the preferred standard. A reserve ship can then cover a sister's lengthy refit or provide surge capacity. Keeping those hulls available helps sustain fleet numbers while extending their useful lives.