Understand the sound
Visual mouth-position guides show what changes from one sound to the next: the place in the mouth, whether air is stopped or squeezed, and whether the vocal folds are on. Put two fingers on your throat and the voicing difference between /s/ and /z/ becomes something you can feel.
Practise without pressure
Make an attempt when you are ready. There is no countdown. Quiet or invalid recordings are detected before analysis and can be retried without using an allowance, so a false start never costs you anything.
Start with visible sounds
The suggested first set favours sounds formed at the lips and teeth, like /m/, /b/, /p/, /f/ and /v/, because you can verify them in a mirror without hearing them. Three at a time is the right number, not ten.
Spot patterns early
Your history helps you notice the sounds that deserve an extra moment of practice, and it distinguishes a sound that is genuinely stable from one that only works right after you have warmed it up.
Know when to move on
A sound is ready to leave behind when it is correct on the first attempt across several separate days, not several attempts in one sitting. Same-day repetition flatters you; the day-to-day record does not.
Carry it into words
Once a sound is stable on its own, word practice puts it back next to its neighbours, where coarticulation starts to reshape it. That is the real test, and it is the next stage on the path.