Here’s what I’m seeing for that procedure
Tighten all bleed screws to 70 inch lb, place clutch pedal in full upright position, fill reservoir, place 15-20 inch hg vacuum on reservoir, hold vacuum for 1 minute, then quickly relieve vacuum, refill if necessary, install cap, depress and release pedal 15 times. Repeat steps above two more times if it doesn’t work the first time.
Is that what you did? Note that there’s no pressurization involved, only placing a vacuum. The reason I ask is b/c the symptom sounds like the clutch hydraulic system hasn’t been fully bled of air yet. The whole scheme seems sort of sketchy to me anyway. Is there an actual bleed nipple on the slave? If so, you may need to disassemble things to that point and bleed the normal way, could work.