If the entire property is not located within the SFHA, then the submission of the plat showing the construction will be outside the SFHA to your vendor should suffice. However, if the entire plat is within the SFHA, then FEMA will have to issue the LOMA before you fund the loan, or you must obtain flood insurance until the LOMA is issued.
Call your vendor and discuss the situation with them. They should be able to guide you in the right direction.
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The opinions expressed are mine and they are not to be taken as legal advice.