Basic corsage instructions would always include the admonishment to hide your mechanics. It's a given that, when finished, your corsage should be beautiful from all sides with no loose strings, silicone pad or ugly glue showing.
It takes a bit to get the hang of gluing corsages, but can be a real time saver. Be careful not to get the glue on your fingers, or it will transfer over to the top of leaves or (worse!) on the flowers themselves.
Don't be afraid to cut your leaves to a proper length. Oversized leaves hanging out of a corsage can take away from the overall effect. Remember the greenery is supposed to ENHANCE the flowers - not overpower them.
Apply glue to the back of the leaves and give a few seconds to get "tacky" before applying them to the corsage.
Decide the placement and don't keep changing your mind. Taking the leaves on and off can create a messy looking design.
If I have several corsages to make, I like doing them all at the same time. This helps make them look uniform and allows one set to be drying while I'm cutting and working with leaves on a different corsage.
I'm placing some of the leaves to the outside edge as well. The placement of your leaves will determine the size of the corsage, since the leaves should just peek out a little beyond the flower heads.
If you get tired of holding the leaves down, simply use a temporary pin to hold the leaves in place while you work on something else.