Lure an Atomic from the left half of the room. Morph in the corner against the top stair and wait for the Atomic to approach. Quickly unmorph just before and freeze the Atomic just after it hits Samus.

Requires:

"f_DefeatedPhantoon"
{
  "or": [
    "h_canBombThings",
    {
      "and": [
        "Morph",
        {
          "obstaclesCleared": [
            "A"
          ]
        }
      ]
    }
  ]
}
"h_canFrozenEnemyRunway"
{
  "enemyDamage": {
    "enemy": "Atomic",
    "type": "contact",
    "hits": 1
  }
}

Exit condition:

{
  "leaveWithRunway": {
    "length": 4,
    "openEnd": 0
  }
}