The simplest analogy for the unity and at the same time threeness of the Most Holy Trinity is ourselves, men, the images of God.
Man is one, yet he generates his word, through which proceeds his spirit. His word and his spirit are not something different than him, his essence and substance.
And the word is the only spiritual relation with the creation, again in the image of God.
Of course, our word and our spirit do not exist hypostatically, we are just images of the Most High.
The Word of God creates and by His Word His Spirit gives Life to matter. We cannot create nor give, but we can innovate and transmit.