Modern web developers rarely start from scratch anymore. Many of us use frameworks such as Bootstrap, Foundation, Skeleton, Initializr and others. These frameworks take the architectural decision-making out of the process, allowing us to focus on more specific design, interface and development questions.
That said, there's still value in creating your own grid from scratch to solidify some of the most elusive concepts behind writing great HTML and CSS.
Challenge: Fork and clone the css-grid-challenges repo, then add CSS styles try to match this design: