Different containers are needed for low centerpieces!
Not all floral designs are in vases. Table centerpieces usually are low on the table so guests can see over the arrangement. I use floral foam to provide stability and nourish the blooms.
Here are examples of containers I use for these situations. One example is to use a small plastic or glass bowl. I use this concept at Christmas for small centerpieces. The bowl completes the design element, but can be upgraded by placing the centerpiece in a more decorative container.
The other example is to use a plastic liner for the arrangement. These liners are sturdy and can be used with decorative containers or baskets. Find a liner that sits flatly in the container. Try not to have too much space between the liner and the container or basket, or too snug. Try not to destroy the liner if it needs to be removed. Cut a piece of floral foam to fit the liner.
Soak the foam until saturated. This may take overnight, depending on the type of foam used. After soaking the foam, place it in the liner and secure the liner with pieces of waterproof floral tape. Place the liner in the container or basket. If the liner is lower than the rim of the container, place a piece of styrofoam in the bottom of the container and place the liner on top.