There is no canvas for the painting of the original singularity; it was the canvas. There is no "outside the universe," there is no "before the big bang;" there is something, there is nothing. The no-thing.
According to Scripture, before the 'big bang', before 'angelic creation',
that 'the Greatest Artist' aka God was from everlasting.
Only God was existing before the beginning of either the invisible spirit realm and the material/physical realm.
-Psalm 90v2