For every non-trivial language $A$ and every finite strict subset $B \subsetneq A$, it's holds that $A \le_m A \setminus B$
As mentioned in the above comment, the format of your reduction is not correct, so you have to take care of that first, and think about it again. Also, the hint I gave in the question that you linked should be enough. Anyway, here is another hint.
Hint: consider the identity reduction that maps every word $x$ to itself, and try to understand why it does not work. Then, think what is the simplest thing you can do in order to fix the identity reduction.