We are usually gone by the time our customers are putting bouts/corsages on. We hope this helps.
The one major rule is they always go on the left lapel. There will be a back and a front to them. The small flower accents typically sit up front. and the greenery are placed on the back showing best at the front.
Photo credit - Monique Sache, email email@example.com
Under the lapel or dress put one pin in sideways capturing the back of the stems
The second pin just captures the stems from the top. Stab it softly downwards into the stem of the bout/corsage. Not enough to go through to the front. This one stabilizes it from swinging side to side.