Come on, it is not that hard.

There is a huge cable attached to the starter motor that goes directly to the battery. There are two small wires and one big one, you need the big one. This is accessible from below but you will get slightly (or maybe even quite) dirty from getting under and reaching in there. But this beats any other method by far in terms of time needed.

Attach a sturdy wire with a "crocodile clip" and then attach a charger. The negative lead can attach anywhere on the body or the motor.

Charging for 15 min is probably enough to get in to the car.

Good luck.

PS Check this link and you will see what I mean.

Google Image Result for http://www.prestolite.com/images_training/fig20-starter-pos-test.gif

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2003 4.4i black ext./black int./black headliner (kid's runabout)
2014 535d X-drive, M package, silver/black interior

Sold but not forgotten:
2009 E70 35d, black ext./black int./black headliner (sold 2021)
2006 4.8iS Le Mans blue/cream int./black headliner, SOLD in 2012 sadly...

Other hardware:
2015 Cayenne S (wife's new DD and definitely wroooommmmm)
2016 Tundra 1794 edition crew cab, luxo hauler
2005 Tundra crew cab, weekend hauler. Sold after 150k very happy miles.