I don't know firsthand how they did the lettering, but it does look like fresh flowers to me too. The way I'm planning on doing it is using a medium gague wire and shaping the inital "A" the way I want it(daughter's name is Audrey)....then I'll use florist's tape and use little clusters of the flowers (taped at the stems to the wire) to cover the wire with the flowers. I'm gonna try a test run to see if it will work with the fresh flowers or not...if not, I'll see if I can find some silk ones that look good...we have a GREAT store here - The Silk Tree Factory - they have the best stuff - from the really cheap flowers that look cheap, lol - to the ones that look just like the real thing. I'm leaning more toward the silk, just because I won't have to worry about keeping them fresh or doing it the morning of the party, and because I'd like to keep the initial as a keepsake and use it as decoration in her room.
Another thing I just thought of is they might have used the florist's foam and carved it into the shape they wanted, then stuck the flowers in and used picks in the bottom to put into the cake....It would definitely stay fresh that way with the foam soaked in water, but I'd have to do it that morning and wouldn't be able to keep it afterwards.
Love to know if anyone else has any other ideas on how to do the initial!