Someone sure had a colourful tie collection.
And with the sheen of most ties, this quilt would really sing, IRL, I'm sure!
LindaSchipper ... I doubt there is a formal pattern out there for this.
Someone just got creative.
As CJSews suggested, it's snowballed corners to get the effect.
With ties having been used, the squares would be smaller than the 5".
Not that the larger size could not be used, it depends on how/big large you want the end result, in order to show the design of the quilt.
Good Luck!