Login screen doesn't show

When I boot hello, it goes through the regular FreeBSD boot process, but then when it gets to the end, initgfx says `Testing X configuration`, then the screen goes black for a second, then I see a bunch of error messages saying
```
(EE) No screens found
```
and then
```
Starting slim...
```
and that's it.

I have to switch to vt1, type in my username, then run these commands:
```
$ ps -auxw | grep X
root 2054 6.7 3.3 386956 240804 v1 S 21:56 5:11.48 /usr/local/bin/Xorg vt9 ...
kettle 3164 ... /usr/bin/grep --color=auto X
$ kill 2054 # or whatever PID the X server has
$ sudo X :0 & DISPLAY=:0 start-hello
```
Anyway, I'm not sure what SLiM is doing, but if I leave it on vt9, then after about 5 seconds I get a black screen and that's it. No mouse, no GUI, nothing.