I figured I'd write a basic installation guide for the people who may not already know how to use Modrinth's pack system.

1. Download and install Prism Launcher from here. If you're using Linux, using the Flatpak version will make your life much easier as it comes bundled with multiple Java versions that you may need for specific Minecraft versions (including the one that this pack is on)
2. Download the pack from here by going to the "Featured Versions" section on the left side of the screen and clicking the newest one that's currently available.
3. Open Prism Launcher and click the "Add Instance" button in the top left, then select the "Import" tab from the options on the left side of the pop up window, then click the "Browse" button and select the .mrpack file you downloaded from Modrinth, then click the "Ok" button at the bottom.
4. After you import the pack, you may need to change the Java version the game will launch with to Java 17. If you're on Linux and using the Flatpak, you already have Java 17, but if you're on Windows you will have to download it manually from here. Right click "Create Hexes 1.x.x" and then click the "Edit" button, then select the "Settings" tab from the options on the left side of the pop up window, then check the "Java installation" checkbox, then set the path to your Java 17 installation path, in my case because I'm on Linux and using the Flatpak, it's /app/jdk/17/bin/java.
5. Finally, sign-in to your Minecraft account by clicking "Manage Accounts" in the top right, then clicking "Add Microsoft" and following the on-screen instructions for how to login via your Microsoft account. Once you've signed in with your actual Microsoft account, you're able to add another offline/cracked account with any username you'd like by clicking the "Add Offline" button. If you don't have an actual Minecraft account, I'm sure there is a fork of Prism Launcher somewhere with this requirement removed or you may even be able to manually add a offline account by editing the accounts file, but I'm honestly not sure. If anyone knows, feel free to post a reply.