@PaulOmen, welcome to HP Forums, this is a great place to get support, find answers and tips.
Thank you for posting your query, I'll be more than glad to help you out.
I understand that you wanted to know if you can install just the SATA hard drive for your OMEN by HP Laptop PC - 15-ax023dx.
Don't worry as I have a few steps that should help fix this issue.
You can install the SSD of your choice, however, HP recommends that you use only the factory shipped HDD & OS, you may upgrade the same at your own discretion, however, the windows OEM may not work and you will need to get a retail version of the windows from a retail store.
If you wish to upgrade the m2 SSD, here's the supported list:
Generic SSD 128 GB 2280 M2 SATA-3 Value TL 827560-027