How to create this shape?

[echo horizon]

P-cccccc:cm------

[quaint merlin]

one corner at a time

[fiery sail]

All shapes can be created with the final operation of pin push, stack, or swap. This shape can be created with ||a swap|| as the final operation.

[placid sentinel]

how do i see what shape that is

[urban lichen]

{P-cccccc:cm------}