Firstly decide exactly what you want the grid to achieve, then chose the appropriate tumble stones – I find it works best if they are the same type in each corner, you can double them up - eg one selenite and one labradorite in each corner. Also a larger one in the middle of the room can really help intensify the intention and keep the energy flowing.
If you wanted to cleanse the space and bring more light in then Labradorite and Selenite together would be perfect.
If you are a sensitive soul and easily impacted by the energy of others a Fluorite or Calcite grid around your main rooms will help to keep your energy clear (I only ever take mine down to cleanse the stones every month or so then put them back again)
When you have chosen your tumble stones lay them out opposite each other around the room (this can also be used across a whole house or around a bed). I think 9 tumbles are a good amount for a powerful grid, but it would still work with 4 if thats all you have!
They don’t have to be exactly opposite each other, follow your instinct, some people make square grids, others triangular, some do the Star of David…it’s open to interpretation (I usually put one in the middle of the room to tie them all together too).
A “layout” is just the same but put around a person.
The idea is that crystals of the same type energetically connect with each other to create invisible boxes which are filled with the vibration, and properties, of that particular crystal.
So, while you go about your daily business they will be busy quietly working away, imbuing your home with their magic.