The Fellow's immediate reporting chain is to a subcommittee of the DSF. Effectively, they're "working" for the DSF (although as a contractor, not as an employee); that committee is responsible for working out if they're doing what they're supposed to do, whether the DSF is getting good value for money, and so on.

The technical board is there to provide decisions on technical issues, whether they come from the Fellows or from the general population. I'd be very surprised if the Fellows didn't regularly identify issues that needed the technical board to render a decision, but the technical board doesn't have any specific control over the fellow.