Work with us on slack to modify a HTML theme to specifications. Ongoing project.

We are looking for someone highly proficient in HTML5 and CSS3 to work with us on an ongoing basis to help create a HTML prototype for our new website. We have purchased a HTML theme which we would like to use as a base for the project.

This is a hands on job so Ideally we are looking for someone who is UK based, simply because of the time differences with international freelancers. However, if your English is exceptional and you work well with the UK timezone, feel free to apply.

Requirements:
HTML5
CSS3
Bootstrap 4
Polyfills for cross browser.
SASS or SCSS
Awareness of current on-page SEO standards.
Good understanding of responsive CSS and UX/UI.
Cross browser and device testing.

Also you are experienced with: Javascript (ES6), VueJS, or jQuery please mention this in the proposal as this could be beneficial.