In the game Kirby and the Forgotten Land, there are 3 secret HAL Rooms to discover. In these rooms, you can collect a lot of coins, or even a figure from the collection! They are bonus rooms and are not necessary to complete the game.
The first room can be found in level 3 of world 1. Make sure you have the adventurer ability at the end of the level. Instead of heading towards the Waddle-Dee cage, go right at the end and try to reach the tree. From there, you can shoot at the targets in the background to unlock a secret passage.
The second room is in level 4 of world 3. Midway through the level, you'll encounter 3 circling robots in the top left of the screen. In the middle of the circle, there's an opening on the side. If you then finish with auto-Kirby exactly 86 seconds later, the HAL letters will appear, along with a ton of coins.
The third room is located in level 3 of world 6. Here, you'll enter a large building at the entrance, which you can't walk around. You'll find yourself in a long corridor with walls that try to squash you. When you reach the end of the corridor, you need to do something special. There are 4 crates in the right wall that you need to break through. After that, you can climb onto the moving wall. From that spot, you need to make your way back to the starting point of the level from above. A ladder will have appeared there. If you climb the ladder, you'll reach the third HAL room, packed with loads of coins!