Michael wrote:
Sure. You'll get a chunk of airspace defined by a block altitude and
maximum distance from some fix or VOR radials.


That is theoretically possible, but not common in airspace that is at
all busy. I do most of my instruction in Houston Approach airspace,

It was not uncommon at all in the evenings for Continental Express
(ExpressJet in this case) to fly off to beaumont and request a chunk of
airspace for them to perform maneuvers and training under an IFR
clearance. Not just a hold, but sometimes an entire quadrant with a 5k
foot chunk of airspace. Granted this was late night, but it was doable.

Dave