Dose here is something of a misnomer. The dose is Zone-2 training. 70-80% of max heart rate, or tested via lactate analysis.
[Edit: On further reflection, I'm tempted to break Z2 up into 2 segments, call them Z2a and Z2b: 65-70%MHR and 70-75%MHR.]
Frequency Attia and San-Millan are in agreement that 4 days per week is probably the sweet spot, that less is ineffective, and that up to 6 days might be beneficial.
Duration: Attia recommends 45 minutes, while San-Millan recommends 1 to 1.5 hours. The difference might be due to Attia doing workouts on a well controlled stationary bike, with San-Millan referring to road riding. San-Millan says at one point something like, 'in the course of a 1.5 hour ride, you might get 1 hour of zone 2.'
Order: Both are in agreement that it is effective to do a bit of high intensity training at the end of a Zone 2 workout, but not the other way around.