Where does narrator hide the corpse in "The Tell-Tale Heart"?

In Edgar Allen Poe’s 1843 short story, The Tell-Tale Heart, an unnamed and “dreadfully nervous” narrator attempts to convince the reader of the narrator’s affection for an elderly housemate, a rich old man who recently died. It’s important to the narrator that he isn’t taken for a madman, though how could he be? What madman could behave so cautiously, and recount their story so calmly, the narrator asks. He loved the old man. He didn’t want his money and had no cause for revenge; the old man had been perfectly polite. There was really only the one problem. The old man had an Evil Eye, pale and blue and filmy. It haunted the narrator to be watched by such an eye, “the eye of a vulture.”

When the narrator killed the old man, it wasn’t without pity. The narrator pitied that the old man had to die and that he had to experience so much terror as he lay in the dark, in his final moments, listening to the hinges of his door creak open. The narrator could hear the old man’s fear as his heartbeat grew “quicker and quicker, and louder and louder every instant.” If the old man’s eye incited all this inconvenience, it was the beat of his heart that precipitated the final blow, “as the beating of a drum stimulates the soldier into courage.”

The narrator reminds the reader not to confuse a gift of acute senses for madness. Wait until you learn of the precautions taken to conceal the crime, the narrator says. The old man’s body was dismembered and hidden beneath three planks of his bedroom floor. There was no blood, which had been caught in a tub, and nothing amiss in the old man’s room. There were, however, police officers at the door, called by a neighbor to investigate a shriek in the night. Fearless, the narrator invited them to search the property, audaciously inviting them to sit in the old man’s room and see for themselves that all was well, the old man was out of town, the neighbor overheard nothing but the narrator’s own nightmare.

The narrator explains that they would have believed him, such was his caution and foresight, had it not been for the sound pounding over the officers’ conversation. Couldn’t they hear it? “They were making a mockery of my horror,” he thought at the time. Unable to bear the noise of the heart and the smiles of the policemen, the narrator confessed, commanding the officers to tear up the planks. “here, here!—It is the beating of his hideous heart!”