We have touched briefly on the practice of creating grids or mandalas with crystals in the article on sacred spaces.
It is best to create your grid in a place where it will not need to be moved or disturbed for a while, so the “altar” or flat surface within your sacred space is a good choice. However, do bear in mind that crystal grids can be as simple or as complicated as you want them to be, and you may want to place your stones in different patterns every time your use them.