My method, using standard, round, laces is to tie a granny knot down hard then put a bow on top and really heave on that. Even if the boow comes undone the granny stops complete loosening.
A reef knot is easier to undo but, with a bow on top it tends to slacken.
BTW, a granny knot is left-over-right - R-o-L; a reef knot is L-o-L - L-o-L. The end retains its identity wherever it is.