The slamming is likely the engine mounts being toast. This era of Mazdas are notorious for failing motor mounts. That wouldn't explain the stalling though. Sounds like something else is wrong and the slamming is a side effect of that. Maybe some more history of the car would help.. I can't tell by your post if you've driven the car at all before this, is the car new to you? Are you new to driving a manual transmission?

 

This is a new car i've bought with the purpose of obtaining my manual's license, however i am not new to manual transmission, however this car has seen a challenge to taking off, my friend who confirmed no knock when taking off in first (successfully) suspects it has something to do with the clutch mostly to do with the gears not being up to speed when the clutch disengages hence why i think the slam is in the gearbox. I simply used my experience of trying to take off and hearing the slamming noise as thats the only time i heard the noise as an example.

 

There are two things that I can think of that are pretty simple that might cause the effect you are getting. One is the clutch pedal itself. There's a plastic bushing for the return spring that wears out and can cause the pedal to stick when released momentarily and in general act strangely. My car had this issue when I got it. The fix was to replace the pedal assembly since the bushing isn't serviceable. The other is there maybe air in the clutch hydraulics. This can make the clutch release very inconsistent and sudden(not able to be modulated, more of an on/off switch).

Here's a clutch pedal-

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