Scorched Slab

1F: As soon as you enter, head straight north. You'll find TM11 (Sunny Day). Grab it, and then continue heading deeper into the slab.

B1F: Once you're on this floor, feel free to use Flash if you have it – it'll make things a bit easier to see. Head north from the entrance and you'll find a Full Heal. After that, backtrack south and take the path heading east. At the next fork, go north. Look for a spot just west of a large boulder at the very end of this path – you'll find an Escape Rope there. Now, head all the way south and take the stairs down to the next level.

B2F: Make your way southeast. You'll find stairs that lead you down to the ground level. Head north from here and get out your Dowsing Machine – it'll ping to a Nugget nearby. Once you've got that, return to the central area and take the stairs in the southwest corner that head west and down.

B2F (continued): Keep heading north and go upstairs. Use your Dowsing Machine again; it should lead you to a Super Potion. Now, head northeast from your current spot and go downstairs. From there, you'll see stairs right next to a Strength boulder – use those to descend to the next floor.

B3F: This floor is pretty empty for now. You won't find much of interest at this stage, but keep in mind that the Legendary Pokémon Heatran can be found here later in the game. For now, your goal is just to leave the Scorched Slab entirely. Head back the way you came.