The greening tape isn't necessary if the foam is a very tight fit and there is no danger of it coming loose from the container.
You can see from the side view I have plenty of foam in which to insert lateral stems of flowers and greenery.
Mixed sleeves of greenery can be purchased. I generally like to choose my own greens, but you can learn to work with any mix of green and get a lovely arrangement.
Cut the cellophane sleeve off carefully with a knife, taking care not to cut the greenery.
Remove or cut off the rubber bands.
Greenery should be cut under water like flowers and stored in a bucket of water WITHOUT flower food. Flower food can tend to turn some greens yellow. Greens are very long lasting and don't need food like flowers do for nourishment.