Well, there is really not much to it. I just went out and dressed this one up a bit. I used and old flag pole as a handle, I removed the duct tape and drilled a hole in the bottom of the container, used a couple of washers and a screw to mount it with. I did just fertilize hundreds of daylilies with it just with the container attached with duct tape and had no problems.
The key is getting the shape and size of the holes in the lid matched to the fertilizer you are using so that it just takes a slight shake to get the amount you want to come out. I show in the photo a slot and a lid with some round holes. The holes may look too large but for the mixture of fertilizer I was using they were about right.
Of course the length of the handle and the size of the container are up to your personal preferences.