Technical SEO is underrated compared to On Page & Off Page SEO; Every SEO Expert or Individual usually prefer On & Off SEO more than other. That’s the wrong move, as your ranking depends upon crawling and indexing. Every search engine like Google, Yahoo, Bing, Yandex, etc., crawls your website, indexes them, and places them in Search result Pages (SERPs) at a certain rank.
The following measure must be focused on while dealing with Technical SEO:

1 – Generate a sitemap and make sure the URLs have a 200 Sucess status code. 

2- You must disallow the URLs you don’t want to be crawled and indexed using Robot.txt. Example In e-commerce Websites ( Disallow: /Cart)

3 – Plan your website structure wisely. Ensure that the last page shouldn’t take more than 4 clicks. If it’s an e-commerce store, then it’s good to go.

4- Always check whether your website is mobile-friendly or not. A good website with mobile-friendly, which increases the Search ranking.

5- Check all Internal Linking are crawlable by a search engine. Make sure they are “Do Follow.”

6- Ensure all the canonical tags are working fine by inspecting if there aren’t non-canonical URLs in the Search console.

7- Speed up your websites and ensure you meet the Core Web Vitals criteria.

8- Set Redirects appropriately; If you have moved your web or a page permanently, use Redirect (301) if temporary, Redirect (302)

8 – Make sure you have correctly set up 301 redirects. It’s permanent. 302 is temporary.

9 – Make sure your site has a proper SSL Certificate Installed.

10 – Set a preferred version of your site. It should open in the same way when accessing it by typing www or without www

11 – Understand the difference between No-index and Disallow; both are different. Use them wisely.

12 – Ensure your website doesn’t have any duplicate content.