Example uses variables set from custom fields also.
$args = array(
'post_type' => 'case-studies',
'posts_per_page' => 9,
'post_status' => 'publish',
'order' => 'DESC',
'tax_query' => array(
array(
'taxonomy' => 'employer',
'field' => 'name',
'terms' => $employer
)
),
);
$the_query = new \WP_Query( $args );