Pop the test tubes into the openings. If they’re loose, secure them with a bit of glue. I went with plastic tubes because they’re safer, especially if you’re planning to add water and flowers.
For spring, I added a budding branch with blossoms made from crepe paper. You could switch this up depending on the season. Summer: Bright flowers. Autumn: Golden leaves and tiny pumpkins. Winter: Evergreen sprigs with mini ornaments. The possibilities are endless!