1. Get out the rubber ball, we’re in solitary confinement.

[Is this sentence grammatical?]

2. Put/place your handouts facedown on the desk.
3. Make the paper facedown on the desk.
4. Have the paper facedown on the desk.
[Which one is grammacal? Do you have some more useful similar expressions?]

1 is a comma splice. There needs to be a sentence break or a semicolon after "ball."

2 is fine.

3 and 4 will be fine when you replace the command verb with "Put" instead of "Make" or "Have."

You could also say, "Turn your papers face-down on your desk."

1. Yes, the sentence "Get out the rubber ball, we're in solitary confinement" is grammatically correct.

2. The sentence "Put/place your handouts facedown on the desk" is grammatically correct.

3. The sentence "Make the paper facedown on the desk" is not grammatically correct. Instead, you could say "Place the paper facedown on the desk."

4. The sentence "Have the paper facedown on the desk" is grammatically correct.

Here are some other useful similar expressions for giving instructions or directions:
- "Set the book on the shelf."
- "Fold the laundry neatly."
- "Turn off the lights when you leave the room."
- "Keep the door closed."
- "Stack the dishes in the sink."
- "Lock the door before you go."

1. Yes, the sentence "Get out the rubber ball, we're in solitary confinement" is grammatical. It is a imperative sentence giving a command or instruction.

2. The sentence "Put/place your handouts facedown on the desk" is grammatical. Both "put" and "place" can be used interchangeably in this context.

3. The sentence "Make the paper facedown on the desk" is not grammatical. Instead, you could say "Put the paper facedown on the desk" or "Place the paper facedown on the desk."

4. The sentence "Have the paper facedown on the desk" is also not grammatical. Again, you could use "put" or "place" to make it grammatical.

Other useful expressions to use in a similar context are:
- Place the book on the shelf.
- Lay the keys on the table.
- Set the laptop on the desk.
- Position the chair next to the window.
- Arrange the plates on the table.
- Rest the pillow on the bed.