This article covers most of what you need -
https://support.us.playstation.com/app/answers/detail/a_id/5006/related/1/session/L2F2LzEvdGltZS8xNDE5NDI0NDMzL3NpZC9XRGxKUEhhbQ==
However, while the article suggests using a 5,400 rpm drive, I would strongly recommend using something faster.
You have three choices, the first two of which will not be quite as fast as you are used to having with a flash drive
1. A standard 7,200 rpm drive, or for more speed...
2. A hybrid 7,200 rpm drive (it has a flash component which is automatically used to store the most frequently accessed data, or for even more speed...
3. An actual flash drive which plugs into the standard 2.5" hard drive carrier
In each of these choices, I would strongly recommend that you choose a large capacity drive, one that is very much larger than your needs. In options 1 and 2, having a very high capacity will mean that the physical accessor movement will be very short resulting in much improved performance. In my main PS3, I have a 750GB 7,200 rpm hybrid drive made by Seagate, which is nearly as fast as a flash drive. My drive is not much more than 10% full, which is one of the reasons why it's so fast. Load times are noticeably faster with this setup than either my second fastest PS3 which has a 500GB 7,200 rpm standard drive, or my slowest PS3 which has an 80GB 5,400 rpm drive.
If you have the budget for option 3, you should know that flash drives become slower over time. The smaller the flash drive, the sooner the speed degradation sets in, and the faster it degrades.
Finally, another recommendation. Buy an external disk drive to backup your PS3's hard drive on a regular basis. I use a 500GB drive in a USB carrier. It's probably a 5,400 rpm drive since speed is not so important. Format it as "FAT", plug it into your PS3's USB port (any one), and run the Backup Utility which under System Settings. When the backup drive is getting close to bring full, delete the oldest backup(s), again using the Backup Utility.
I have only once needed to restore my PS3 from a backup. That was a good lesson!
If you are paranoid, and you should be, you will plug the backup drive into your Mac or PC and make a copy of your most recent backup onto that computer.
"There are two types of drive in this world. Those which have failed, and those which are going to fail."