@settings(defaultLengthUnit = yd)

tri = startSketchOn(XY)
  |> polygon(radius = 3, numSides = 3, center = [0, 0])
  |> extrude(length = 2)

// Get the plane which `tri` ends on.
p0 = planeOf(tri, face = END)

// Offset that plane by 2, then draw a square on it.
startSketchOn(offsetPlane(p0, offset = 2))
  |> polygon(radius = 2, numSides = 4, center = [0, 0])