When loading slick slider in collapsed content (angular-bootstrap collapse plugin in this case) the .slick-track div gets 0px width, resulting in the slider trying to fit al
Finally I got the answer by slick creator Ken Wheeler himself. When collapsable content is triggered open, simply call the following line:
$('.slider-class').slick('setPosition');
...and replace "slider-class" with the class name of your slider. Personally I created an angular function with this line, and triggered it with ng-open.