It's easy.

Enforce the existing laws about hiring illegals with
fines, and if necessary, jail terms.

In key industries like agriculture, where a sudden shut-off of foreign labor would
cause severe economic dislocation, formal guest worker programs could
be instituted which would not only control the flow, but also ensure that the
workers weren't subject to inhuman working conditions at the hands of unscrupulous
employers.

Business is finding it very profitable to exploit illegals and further
uses them to keep downward pressure on everyone's salaries.
That is why the Republican Party is so split on this issue; all this talk of walls,
border guards, amnesty, how much the illegals contribute, compassion,etc
is hypocrisy and smokescreen.
If someone wasn't getting rich off these people they wouldn't be here.
Follow the Money.