The ornamental design for a foldinglayoutstick, as shown and described.
FIG. 1 is an isometric view of a folding layout stick showing my new design.
FIG. 2 is a top view thereof.
FIG. 3 is a left side view thereof.
FIG. 4 is a front side view thereof.
FIG. 5 is a rear side view thereof.
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a right side view thereof.
The broken line showing of some structural features are is included for the purpose of illustrating non-claimed subject matter and forms no part of the claimed design.