Measure the height of your glass container with a measuring tape or ruler so you can calculate how long your flower stem must be for it to be completely submerged. With sharp scissors, cut your flower stem to the proper length to be submerged. Remember, you will want to fill the container 1/2 half to 1 inch from the top rim with water.
Put a dab of aquarium silicone glue on the bottom of your flower stem, then stick the glue end of the stem to the inside bottom of the glass container. Follow the instructions on the aquarium glue for drying. Aquarium glue does not contain any harmful chemicals. As an alternative to gluing, which is difficult to remove, you can purchase small fishing weights and clear line at a sporting goods store. Use the clear fishing line to tie the weights to the bottom of the flower stems. If you do not want the weights to show, add a layer of small pebbles or marbles to the glass container.
Check the position of your flower or flowers in the glass container to make sure they are exactly as you want them and make sure it is not too crowded. It is better to have the flower or flowers correctly positioned before adding the water. Movement of the flowers once they are submerged may damage them. Since the water will magnify your flowers and any imperfections, check for loose or exposed fishing line or other flaws on the flowers.
Fill the glass container with your flowers using distilled water. Tap water will cause bubbles to form on your flowers, taking away from the visual affect. Distilled water will remain clear and bubble free.