Does the prohibition of a man putting on his sandals while standing imply tahrim (prohibition) or karaha (dislike), and has anyone ever stated that it is haram (forbidden)? And is it obligatory for a man to sit down to put on his sandals, even if it's on the ground if he can't find another place?

It was narrated from Abu Hurayrah that standing while putting on sandals is disliked, and the people of knowledge explained this as due to the fear of hardship. Ibn Muflih mentioned on the authority of Imam Ahmad that nothing has been authentically reported regarding putting on sandals while standing. It was narrated from Aisha that the Prophet, peace and blessings be upon him, used to put on sandals both standing and sitting. Therefore, the matter is flexible.