Is there anything wrong with putting up a cholent to cook right before Shabbos?
The Gemara is concerned that if people leave a pot on the flame starting Friday afternoon, a person may get impatient for his dinner and stir the pot around on the flame, or play with the flame, to get it to cook faster.
The normal recommended alternative is if you want to leave a pot cooking from before Shabbos, you must make sure the food is at least 1/2 (some say 1/3) cooked before shabbos begins, that way, it's already "minimally edible" and hence "cooked."
Another option suggested is to take something large, raw, and needing a long cooking time, and putting it up immediately before shabbos -- you have no hope that this will cook in time for dinner Friday night, no matter how you play with it, so you'll leave it until the next day.
By this logic, if someone had a large pot of cholent containing large chunks of frozen (raw?) meat and raw potatoes, if an hour or so wouldn't be enough to cook it, it could be put up right before Shabbos.
Major caveat: Rabbi Yosef Eliyahu Henkin, the premier halachic authority of America for several decades in the early-to-mid 1900s, felt that a "will take too long to cook" setup as described by the Gemara didn't pertain to today's kitchen appliances, so he felt this option was no longer available. (This appears in the Ezras Torah calendar, which follows his rulings.) I don't know which other rabbis say what.
Shulchan Oruch Harav rules that one may put raw meat (beef specifically, which takes longer to cook) into a pot and into an oven to cook slowly just before Shabbos. The reasoning is that since it will take a long time to cook, a person will not come to stoke the coals, or otherwise interfere with it and desecrate Shabbos - he knows it needs to cook the entire night.
On the other hand, placing raw meat into an oven to roast would be not permitted since it takes less time to cook and will become edible that evening. There is then a danger that a person might forget that it's forbidden to interfere with it and come to desecrate Shabbos.
It would follow that it is permitted to put the cholent in a slow cooker just before Shabbos, if it contains raw meat. A slow cooker on a low setting takes 6-8 hours to cook a cholent.
EDIT by sabbahillel Note that one must tape over or disable the control knob so that the setting cannot be changed once it is plugged in. This would prevent it from being turned up or down during Shabbos.
Either way, it is best to consult a competent orthodox rabbi. Try askmoses.com or chabad.org