All perfect praise be to Allaah, the Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
Abu Hurayrah reported that it is disliked for a man to put on his sandals while standing. However, scholars explained the rationale for it being disliked is the fear of suffering difficulty and hardship. This was highlighted by ‘Abdur-Razzaq as he said "It is disliked to put on shoes while standing so as to avoid hardship." [Al-Musannaf]
Ibn Muflih reported the following on the authority of Imaam Ahmad "There is no evidence regarding (the impermissibility of) putting on shoes while standing. Abu Muhammad Al-Khallal reported the following on the authority of ‘Aa'ishah 'the Prophet, sallallaahu ‘alayhi wa sallam, used to put on his sandals while standing or sitting down.'" [Al-Adab Ash-Shar‘iyyah]
From what we have mentioned above, it is clear that there is toleration in this matter and that a Muslim may put on his shoes while standing even when he finds a place to sit to put on his shoes.
Allaah Knows best.