This is not the way it tells you in the manual but....................
Pull back the carpet and underlay and set the brake pedal height between the bottom of the pedal and the floor to 6 & 7/8"
Set the clutch pedal level with the brake.
Push the clutch operating arm rearward until the release bearing touches the pressure plate and make sure the arm is one spline forward from vertical. Remove the arm and move it on the splines if it's not, and take care not to drop the nut in the bellhousing.
Pull back the slave cylinder boot. Adjust the pushrod so that the piston is about 1" away from the circlip. (Pedal at rest)
Wind the stop bolt all the way in. (Thats the one in the footwell.)
Then get someone to slowly depress the pedal as you look at the piston in the slave. What you need to get is the piston just touching the circlip when the pedal is on the stop, and you achieve this by adjusting the pushrod each time just before the pedal is depressed.
Once you get to the point that putting your foot on the clutch down to the stop makes the piston touch the circlip in the slave, lock the nut on the pushrod.
Then wind the stop bolt up one turn, and lock it with the nut.
Depress the pedal again and make sure there is at least 25thou clearance between the piston and the circlip in the slave.
If not wind the stop bolt up some more a turn at a time.
Refit the carpet and IIRC that's it.
Road test.
If it still slips I'd suspect either the release bearing sticky in the housing, or the clutch pressure plate being slow to clamp the centre plate. (That's if it only slips after you've used the clutch.) If it slips all the time, chances are the box is going to have to come out again.
If I think of anything else on setting it up I'll add it later, but I think I've got it all there.