Done this many times and even in the paddock at a meeting when i broke 2nd gear.
I have my knees under the bell housing and the tail above my chest then as the gearbox comes back off the spline gentle lower my knees and bring the box down onto my legs and chest.
It is then a bit of a wriggle to crawl out to towards the rear of the car, letting the box onto the ground. It can then be dragged out sideways.
Refitting is the reverse.
You do have to drain the oil otherwise you get a facefull of it (not that this has ever happened to me
)