The antonyms for the phrase "press together" could be "pull apart," "spread out," "loosen," "disperse," or "separate." If we imagine two pieces of clay, pressing them together results in a compact and consolidated form. However, pulling them apart makes them separate and distant from each other. Similarly, when people are asked to press together, they are usually encouraged to maintain close proximity to one another. Whereas, spreading out could mean creating more space between individuals, objects, or things. Depending on the context, the use of antonyms can give opposite meanings, such as in working out knots in muscles, we apply pressure to press together, and release or relax pressure to pull apart.