Aqṣā al-ḥalq is the deepest part of the throat, furthest from the mouth. It articulates ء and ه, which share a region but not an identical sound.
ء: begins with a distinct glottal closure/release, as in أَنْ.
ه: is a gentle, audible breath-like consonant, as in هُمْ.
Practise the consonants separately and then within short syllables. Turning hamzah into a soft ha, or pronouncing ha with hamzah's abrupt closure, confuses two separate letters.