Place [4321] at the same time, or any order except starting from one end and working up/down eg [23] then [14] or [14] then [23] or [13] then [24]. Play 4,3,2 *Place 3 under Play 1 Place [21] Play 3,2 Repeat from *
Reverse for downwards 123123…1234
If you have trouble consider particularly if your fingers are too high or thumb/elbow too low.