I almost posted this earlier, but figured it wasn't that mind blowing. Its not necessarily the letter combos that make those sounds, its their relationships to the vowels in the words.
just do the thing where they all line up and turn your hand sideways and all your fingers will be at different elevations which is why, its physically impossible but imagine moving your knuckles to all the same height and all your fingers would be at different heights
so when your hand is open all your knuckles are level like that -----
and when its clutched all your fingers are level -----
thats at least what i came up for as an explination last night