Place a casket in the center of the set. This is your set piece. The rest of the scene will revolve around the casket.
Place benched pews to the left and the right of the casket for grieving mourners. The pews need to be out of the way of the casket, as your main action will take place in the front. The pews will face the casket. This will give the illusion of a large church without getting in the way of the audience.
Add mourners to each row of pews. The mourners should be sad, wearing black, and giving off a generally somber tone. These actors are more for effect than anything. Having mourners in the pews will give the atmosphere of sadness and make the scene more genuine.
Place decorative flowers around the area of the casket. Add a wreath with a picture of the deceased placed on a stand to the left or right of the casket itself.
Place a podium and a religious figure directly behind the casket. The podium is elevated above the casket so the audience can see the religious figure speaking and the casket set piece is still visible.
Play somber organ music in the background. Don't make the music so loud that it drowns out the actors, but it should be loud enough to be noticed.
Place heavier lighting above the casket with little to none in other areas. The audience will draw its attention to the casket, and the rest of the scene will fade in behind it.