In order to hollow out the bulb, please check out my guide titled "How To Hollow Out a Lightbulb"!
These are all of the materials you will need.
Here are the rubber pads to support the lightbulb.
First, start with a long lightbulb, I found this at my local hardware store.
Now add 4 of the rubber pads to the bottom of the vase. I recommend putting them on and seeing if the bulb sits how you want it. If so, hot glue them to the base to ensure they will stick properly.
Now cut them stem of your flower to fit into the bulb.
Add water, and there you have it!