Here’s how to create a custom single post:
1. Go to WordPress Dashboard.

2. Select PostX, then Go to Builder.

3. Select Add Singular.

4. Select Start from scratch (if you want to make it from scratch) or Import a template (if you want a premade template).

5. Name your Template, then Click the plus icon (toggle block inserter), Add your desired Blocks to create your page.

6. Now hit Publish. You will see a popup box of “Where Do You Want to Display Your Template?” Here Select Include; Select Posts and then select All (You can add multiple conditions by clicking Add Conditions). Select Save Condition and Exit the Popup box by clicking the Cross (X) button.

7. Click Publish

And you have successfully created your custom single post.