Suppose the height of the person is : h units.
Place the mirror of height h/2, on the wall, nailed with the top of the mirror at a height of h above the floor. So the mirror is vertically on the wall from height h to h/2.
The rays from feet and above hit the mirror at the bottom of the mirror, and then meet the eyes of the person.
The person can see the reflection / virtual image in this.