Answer:
Emily is alluding to the "house" which was her grave. She is giving a description of her grave, like she's describing her house where she will be living.
Step-by-step explanation:
Emily Dickinson's poem "Because I Could Not Stop For Death", she talks of dying and how death feels like. She laid emphasis on the identity of death, personifying it as a gentleman who had come to take her in a carriage.
The lines in the question are from the 5th stanza of the poem. Here, she is alluding to her grave as a "house", which was "a swelling of the ground", just how graves are like a stump in he ground, a bit elevated. Being on the ground, "the roof was scarcely visible" and the 'cornice', a bit of hanging just below the ceiling, was also "in the ground".