Freelancer required on hourly basis to create project functional and technical design document

Freelancer required on hourly basis to create project functional and technical design document. He will create High level design, low level design, Test cases, Flow/UML diagrams and all required docs. Must be good in documenting and answering questions. The Web application will be built in asp.net core and mssql and the related technologies.
Must be available for minimum 4-5 hrs per day to discuss and document.