Here are the hackling instructions for the Mahony (correct spelling) from our book Steelhead Fly Tying Art and Design. As you can see Dec secures the hackle by the root/butt end.
Step 4. Select a black schlappen hackle with barbules of sufficient length—sufficient meaning as long as you can find! Clear all the fluff and unusable barbs from the stem. Strip the barbs from the right side of the feather. Moisten the barbs and work the feather until the barbs disengage and no longer hold together. Secure the schlappen hackle by the stem on the back side of the hook. The “good” or convex side should be facing you.
Without the photo the instructions are incomplete. Will have to do better on the next publication.
Traditionally speaking the hackle for this style of fly is tied in tip first at the eye of the hook, then palmered to the bend of the hook. The oval tinsel, which was secured in at the bend of the hook is them wrapped forward trapping the stem of the hackle to the hook. The hackle having been counter wrapped is now secured with multiple turns of ribbing. In more modern times the standard Woolly Worm was tied using this same hackling technique, were as the Woolly Bugger is hackle tip first from the bend of the hook. For most of my steelhead work I use the tip of the hackle secured in at the bend. I never really got into the spey style of tying.
Here are some more of the instructions for the Mahony and a shot of the completed fly. Dec uses a little muscle to tame his body hackles.
Step 10. Wrap the schlappen hackle forward, following the rearward edge of the oval tinsel. The barbs of the hackle should be flowing toward the bend of the hook. If the barbs are coming out at right angles and even slightly forward, don’t worry. The next step explains how to fix that.
Step 11. With your left hand, pull all the barbs rearward. With your right hand, give the hackle stem a good pinch. This will lock the barbs into position and flowing back toward the bend.
Step 12. This photo shows the completed body with the hackle in proper position after the pinching technique.
As you well know Dec has a lot of confidence in this style of fly. Good reason, it works. The only issue is finding the hackle. We went through 6 packs of schlappen to find the feather for this step by step. Dec's preferred hook for this fly is Alec Jackson's 1.5. Finding hackle for the smaller hooks is not a problem, 1.5s and 3/0s is a problem. We go over all the different hackling techniques in the book. We have a few copies left, you can find it in all the fine fly shops or on our web site, atthevise.com (sorry for the shameless plug). I got to meet Jerry Mahony a few weeks back up on the Skagit. It was fun to hear his stories of fishing the Skagit and Sauk back in the day. Great to be able to connect a face with Dec's red spey style creation.
Old step by step for the Blue Butt Black Mahogan https://www.speypages.com/speyclave/...k-mahogan.html