Here is a 3x12 workout example on the HighNorth website:
Source: How to improve your lactate threshold as a cyclist — High North Performance
That is along the same lines as my coach prescribes. I’m very happy with this style of workout with driving adaptations to raise threshold.
FWIW my Garmin 530 classifies these workouts as Threshold, this is from a two hour workout with 3x8 at 85%/115% (1:3 ratio, so 3-min at z3 and 1-min at z5):
