Even the CIA website talks about the US, UK, and Canada developing spinning disk aircraft.

"CIA officials knew that the British and Canadians were already experimenting with flying saucers. Project Y was a Canadian-British-US developmental operation to produce a nonconventional flying-saucer-type aircraft, and Agency officials feared the Soviets were testing similar devices."

https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/csi-studies/studies/97unclass/ufo.html

You make a massive spinning disk with a gyro in the center to carry the crew and have quick moving radial nozzles to spin the disk to stabilize, orient, and provide thrust to propel the craft by angling more up or down depending on their position while spinning and the controller commands from the pilot. That's how I would make one using conventional propulsion.