1. Of two or more people or things, to lie or recline alongside one another. (A common miswording of "lie together.") We laid together in the grass, watching the clouds pass by overhead. All of the timber we'll need is laying together in a pile behind the shed.
2. old-fashioned euphemism Of two people, to have sexual intercourse. (A common miswording of "lie together.") He kept trying to spread rumors around school that he and Jill had lain together at the party, but everyone knew it wasn't true. This was back in the time when a woman could face public shaming and condemnation for laying together with a man before marrying him.
3. To place two or more people or things in a reclining position alongside one another. In this usage, a noun or pronoun is used between "lay" and "together." Just lay those beams together in the bed of the truck so we can haul them away later. We had to lay the wounded soldiers together in groups of four because of how crowded the medical hall had become.
lay something together
to lay things side by side. Lay all the logs together and stack them as high as you can. Lay the red ones together and put all the others over there in a pile.