These instructions can be used in several small scales, as you're working from an in-scale sketch rather than fixed measurements. Please visit my garden center for an overview of all my free flower DIYs and other files about making flowers.
The supplies listed should work from N (1:160) up to H0 (1:87) scale. (In 1:48 you'd probably get the best effect from quite different methods, like using punches for both flowers and leaves, but you could also glue multiple crunchy flower bits around the wire, and cut fringe style leaves for the top and to wrap around the stem). The flower supplies page has more information on supplies you can use.
Pour out some crunchy flowers from the package, and pick one with a shape similar to the lily's ring of flowers.
Glue it to the top of the wire.
Put a dab of glue on top of the flowers, and dip it in the leaves.
Apply glue to the part of the stem that would have leaves. Dip it in the leaves.
Let your flowers dry thoroughly before planting them.
The leaves should really be narrow rather than rounded, but at least I think these punched leaves look better on the lily than green foam would. To improve the look, you could cut the leaves for the top in half (with a scalpel or Xacto on a cutting mat), and apply them one by one with tweezers.