In the aforementioned pasuk it says: ויעש העץ – “And he made the gallows”. The advice given to Haman was: יעשו עץ - “let gallows be made”, why did Haman make it himself?
The Alshich explains: His wife and all his friends told him that the best thing for him would be for Mordechai to be wiped out. However, they cautioned him, that it was below his dignity to be personally involved in the whole sordid process. Therefore: יעשו עץ - “Let gallows be made” — by artisans, and: ויתלו את מרדכי עליו - “The executioners will hang Mordechai on it.”
Chazal tell us that: שנאה מקלקלת את השורה - “Hatred disrupts the correct order of things” (Rashi to Bamidbar, 22:21), and people deviate from the norm when acting out of hatred. Consequently, Haman who hated Mordechai with a passion did not wait for any workers, but immediately: ויעש העץ — he personally made the gallows.
