Answer: There are two methods that could be called stacking. One is to plant several layers of bulbs in a single pot,chill them for a set number of weeks and then bring them into a warm bright area to force them into bloom. This can be done with all one type of bulb or with a mixture of larger and smaller types, but they should require similar "forcing" procedures in order to bloom successfully.
The other method is to plant several types of bulbs in one area of the garden so that there is a succession of blooms. Small crocus bulbs for instance can be planted over top of later blooming spring bulbs such as daffodils or tulips or even "forgotten lilies" (Lycoris squamigera) for bloom in late summer. Gladiolus could also be added to such a planting.
True lilies (lilium) are perennial bulbs that are a bit sensitive to root disturbance and competition, so I would not suggest using them in a densely planted area with a possible exception of the little and undemanding minor bulbs such as crocus around them.
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