Building a Crypt Room with Sarcophagus and Coffins
Shell out the room
Start with a rectangular chamber. Use Dark Iron Block for the walls and floor, and leave one wall for a Dark Iron Door entrance. Cut windows with Dark Iron Bars and add a Dark Iron Trapdoor in the ceiling for a ladder shaft. This gives you a sealed, mod-consistent crypt.
Place the Sarcophagus
Set a Sarcophagus as the centerpiece, either against the back wall or in the middle of the floor. It is the largest single burial block in the set, so give it clear space on all sides.
Arrange coffins
Line coffins along both side walls. Use one wood type per row for a clean look — Oak Coffin and Spruce Coffin on one side, Birch Coffin and Dark Oak Coffin on the other. For a nether crypt, use Crimson Coffin and Warped Coffin. For a jungle ruin, use Jungle Coffin and Mangrove Coffin. Leave a walkway down the middle to the Sarcophagus.
Add remains and light
Place Skeleton Hand and Wither Skeleton Hand on ledges, and stack Skull Pile, Skull and Rib Cage, Skull on Pike, and Torso Pile in corners. Use the wither variants for a second, colder room. Light the space with Soul Fire Brazier for a blue tone or Fire Brazier for warm light, and set Candle Holder beside each coffin. Finish with Glazed Urns or Small Urns tucked between coffins.