Slick slider how to enable ajax-loader.gif?

Question

JavaScript

Slick js and slick css files are included via cdn.
The slick-theme.css contains the following code:

/* Slider */
.slick-loading .slick-list
{
    background: #fff url('./ajax-loader.gif') center center no-repeat;
}

Put this ajax-loader.gif in the root. Enabled lazyload lazyLoad: "ondemand". It was expected that until the file was loaded, this loader would spin, and instead of it we have just an empty square. The question is how to make it so that this loader is displayed or nothing is displayed at all until the files are loaded.