  We describe an experimental setup for producing a large cold erbium (Er)
sample in a narrow-line magneto-optical trap (MOT) in a simple and efficient
way. We implement a pair of angled slowing beams with respect to the Zeeman
slower axis, and further slow down atoms exiting from the Zeeman slower. The
second-stage slowing beams enable the narrow-line MOT to trap atoms exiting
from the Zeeman slower with higher velocity. This scheme is particularly useful
when the Zeeman slower is at low optical power without the conventional
transverse cooling between an oven and a Zeeman slower, in which case we
significantly improve the loading efficiency into the MOT and are able to trap
more than $10^8$ atoms in the narrow-line MOT of $^{166}$Er. This work
highlights our implementation, which greatly simplifies laser cooling and
trapping of Er atoms and also should benefit other similar elements.
