You need to correct your step 2 make as below, Keep requirejs-config.js file in root of your theme instead of web folder.

Create requirejs-config.js file in

app/design/frontend/_YOUR_VENDOR_/_YOUR_THEME_/

with the following code in requirejs-config.js

 var config = {
    paths: {
        slick:        'js/slick'
    },
    shim: {
        slick: {
            deps: ['jquery']
        }
    }
};

Run

php bin/magento setup:upgrade

 

php bin/magento setup:static-content:deploy

You need to correct your step 2 make as below, Keep requirejs-config.js file in root of your theme instead of web folder.

Create requirejs-config.js file in

app/design/frontend/_YOUR_VENDOR_/_YOUR_THEME_/

with the following code in requirejs-config.js

 var config = {
    paths: {
        slick:        'js/slick'
    },
    shim: {
        slick: {
            deps: ['jquery']
        }
    }
};

Run

php bin/magento setup:upgrade

php bin/magento setup:static-content:deploy