Pour your material into the container, to a depth of 1–2 inches (2.5–5cm). Place the flowers upright in the material, making sure they're stable. Sift or slowly pour more desiccant on top of them, until they are buried.
If using sand, you don't need to bury the flowers completely. The sand is mostly for support, and air exposure can help dry the petals. Flowers from the daisy family dry best upside-down instead. Some flowers, such as snapdragons and delphiniums, dry best when laid horizontal. If the stems are still attached, fill the container as deep as necessary to hold them.