There is no option for product image slideshow for Boundless theme. So i decided to create one using the same slick plugin that powers the slideshow/hero section and an alternate product template. Theme version is v9.0.17

  1. Create a alternate product template product.image-gallery.liquid

  2. Create a product template section product-template-gallery.liquid and rename the default section inside alternate template you created above - {% section 'product-template' %} to {% section 'product-template-gallery' %} . See screenshot below

  3. Replace the code inside product-template-gallery with this Gist

  4. Initialize the sliders inside theme.js.liquid. See screenshot below

    dots: true,
    infinite: true,
    speed: 500,
    slidesToShow: 1,
    slidesToScroll: 1,
    arrows: false,
    asNavFor: '.product-slideshow-nav'

    slidesToShow: 3,
    slidesToScroll: 1,
    infinite: true,
    asNavFor: '.product-slideshow',
    dots: false,
    arrows: true,
    focusOnSelect: true,
    nextArrow: '<button type="button" class="slick-next">&raquo;</button>',
    prevArrow: '<button type="button" class="slick-prev">&laquo;</button>'


Add some custom styles for the arrow buttons inside theme.scss.liquid and select the newly created product template inside product admin. Done!

    top: 42%;
    font-size: 2em;
    right: -5%
    left: -5%

This solution is taken from - How to show Product Image Gallery on Product Page (Boundless Template)