A flow control method and assembly for an oil or gas well comprises generating a pressure signature in the fluid in a bore of the well comprising a minimum rate of change of pressure, and transmitting the pressure signature to a control mechanism to trigger a change in the configuration of a flow control device in the bore in response to the detection of the pressure signature in the fluid. The flow control device can comprise a barrier, such as a flapper, sleeve, valve or similar. The pressure signature is transmitted via fluid flowing in the bore, typically being injected into the well, optionally during or before frac operations, via fluid being used for the frac operations. The control mechanism typically includes an RFID reader to receive RF signals from tags deployed in the fluid flowing in the bore.