In the Ichiyo School of Ikebana there is no formal miniature arrangement training. Instead, the same principles that one uses for larger arrangements are used in smaller arrangements except for modifications as needed for the smaller size.
As an example, in the first arrangement a student makes--the moribana upright--there are only three stems (branch material) and three flowers. One can apply the same principles in making this arrangement when making a miniature arrangement. However, due to the smaller size, one may leave out the second or third stem or both of them. Of course the flower materials need to be of the size to correspond to the container.
It may be difficult to also find materials for these smaller arrangements in places which sell flowers. However, many times field materials may be harvested close to home. The flowers used in these miniature arrangements were actually clipped from an open field near my home. The arrangement above with the white ramekin and brown mat (shikimono), has daisies, and an unknown "weed". The arrangement with the black ramekin and white shikimono has clover and birdsfoot trefoil. The arrangement next to this paragraph has a common grass and crown vetch. Lastly, the arrangement below with the small brown vase has only clippings from a red-twig dogwood bush found in the open field.