Can we build a cheap/fast border fence like Hungary did? From Wikipedia: https://en.wikipedia.org/wiki/Hungarian_border_barrier

In 2015, Hungary built a border barrier on its border with Serbia and Croatia. The fence was constructed during the European migrant crisis (see timeline), with the aim to ensure border security by preventing immigrants from entering illegally, and enabling the option to enter through official checkpoints and claim asylum in Hungary in accordance with international and European law. The number of illegal entries to Hungary declined greatly after the barrier was finished.

They keep all the asylum seekers on the outside of the fence where they can wait. When they get tired of waiting, they go away.