How to get my dirt to not turn into a grass block?

So I made a flat world and I use it for displaying every single block and item in the game using the order of the creative inventory (excluding items accessible via commands). A certain order is dirt blocks and different types.

In the order, a certain bit of it is Dirt, Coarse Dirt, and Grass Block. They are all beside each other, and that’s what I like. However, I’m worried that the dirt will turn into a grass block even if the coarse dirt is in the way. So I set it the Random Tick Speed to 1000 (enough to make a fast process of turning it into a grass block without making it too laggy due to high tick speed).

So I thought of ways to overcome this:

1. Remove the block under the dirt block. Didn’t work.
2. Place the dirt in y = 5 (assuming everything else is in y = 4). Works, but I don’t want this. I want every block and item on y = 4.
3. Place something on it. Transparent items won’t work, but other blocks and water works, but I don’t want this either. I want to walk on the blocks with no obstruction.

This list will continue to be updated as response to answers given.

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Then I found this answer on a question having the exact opposite goal. All the blocks and items are located in the same X-level to actually be viewed in front of the player spawned Also, the given 1st rule in the image is not something I want to do. I kept the world Always Day to shine everything with a bright sky for better display, and I also want to record a video of me walking on the line of blocks and items.

I thought of using commands, but I can’t be sure if /setblock would even help stop the block from turning into something else.

Are there other ways on how I can stop my dirt block to turn into a grass block?