Creating your own mock exam is entirely doable. I've extensively shared before on my Tiktok lives that I often do my own timed practice at home leading up to the exams.
Here are some tips that you can follow:
1. Simulate the real environment as much as you can
I don't mean that you need a teacher to be pacing back and forth going clop clop clop...
Find a quiet location that has little to no distractions. Your actual exam will be a quiet space, so you'll have to get used to focusing on doing your own mock paper the same way. That means no music too, so put your airpods away!
2. Allocate the same amount of time as your real exam
This goes without saying. You'll need to hone your exam skills to be able to perform within the given time. Set a timer to make sure that you keep to the time limit. You do not need to be extremely obsessed with whether you can finish your paper at this point. Try your best, and see how far that takes you.
If you can't finish the paper within time limit, ask yourself which are the areas that you need to improve on. Then keep trying. When you're fully prepared, you will find that you can finish most papers within time limit, as they are usually designed to be completed within the set duration.
3. Marking your paper
You should be able to mark your own paper. Answer keys to prelim papers can be easily found online. If you're stuck, ask a friend, consult your school teacher, check with your tutor, or simply..
... call me. I don't offer marking services, but I might be able to help you with some of your weaker topics.
4. Select the right paper for yourself
In case you haven't realised, I do something called the Prelim Paper Review (PPR).
You can gauge which papers are suitable for you based on the matrices I used.
The video versions can also be found on my Tiktok. I also have a telegram channel where I post the summarised versions. You'll also be able to quickly filter through the various reviewed papers to find what suits you.
Why does creating your own mock exam work?
Having your own mock exam actually counts as active recall. This is also known as the "testing effect". Over time, you will realise that you can conjure the information you need more and more easily.