As Alec would say, "It depends on the size of the fly and the number of body segments". Usually Alec uses 3-4 Ostrich herls per segment. Don't forget to tie in a piece of oval (not wire) tinsel (use gold with red, yellow, or orange, silver with everything else)along with the ostrich at each body segment.
Put a Thompson style hackle plier (the kind with the rubber pads on each side) over the ostrich and oval tinsel, then spin the hackle plier clockwise until you have a nice herl-chenile (it will look like chenile when it is spun the correct amount). Wrap the ostrich chenile body segment and tie it off on the bottom of the fly. Tie a hackle in by the tip, double it as you wrap it by using the finger and thumb of your left hand (right hand if a left-handed tyer) to pull the hackle barbs back toward the bend, and after 5 to 7 wraps of hackle tie it off on the bottom of the hook. You have to do this for each body and hackle segment, which is why it can take a while to do it on large hooks. And the number of segments varies with the size of the hook; but should never be fewer than 3 (which is what an Alec Jackson #7 Spey (#6 or #8 for regular or low water salmon irons) hook would use. An Alec Jackson #1.5 hook would use 5 segments and an Alec Jackson #3/0 would use 6 segments.
Hope this helps all who wish to tie Alec's Sauk River Grub style flies.