12 weeks is still very young. Don't panic. The argument that dogs won't soil where they sleep only works if they have an alternative -- i.e., they can walk to the other side of a play pen and go. Or, B, you let them out of the crate every hour. Their bladders at 18 weeks have a 2-hour capacity.
I'm an advocate of Ian Dunbar and
Dog Star Daily.
In it, they have a section on errorless housetraining:
Errorless Housetraining | Dog Star Daily.
Ian also has a podcast radio show, and this 30-minute episode discusses the same thing:
audio by title episode 4 - errorless housetraining chewtoy training | Dog Star Daily
In a nutshell, here's what the site advocates:
When away from home for more than an hour or not directly supervising them, keep them in an x-pen or small playroom. It should include:
* Bed/crate
* Water
* Chew toys stuffed with treats.
* Doggie toilet in farthest corner away from bed area.
The dog should stay in that longterm play area at all times you're not directly supervising them.
When you ARE directly supervising them, don't turn your back on them. Take them out every hour on the hour and reward with three liver snacks for success outside.
If this sounds like something that would work for you, definitely check out the site. I'm leaving a lot out. Good luck.