All you front end devs who work with dedicated design teams, what's you usual workflow? Do the designers pass on the UI kit with all the assets and dimensions and you clone the thing using whatever stack you're using or do you all decide the specs on the fly looking at the general visual structure of the design?

They design according to customer specifications then show it to us, we give input (removing overcomplicated things for example but also a set of fresh eyes), then it goes to the customer. We use invision so I can checkout both mobile and desktop designs. I eyeball everything until I get it almost right without to much work for pixel perfecting everything.
Go back to the designer and discuss it. Some things might be tons of work to make it according to design but look good as is as well, in that case we can just keep it and the designer will change the design accordingly.

Repeat until satisfied...

This is a general workflow I have used in multiple companies. By going to the devs before going to the customer is especially good because changing major things is difficult after the customer approved a design.
Most of the time the above is component based.

@Codex404 Ohh okay. That makes so much more sense. I'm a total noob at frontend but since there's no one to do it, I was tasked with it anyway. And the designer just send me a design (which is complicated to me probably because of my incompetency) and asked me to implement it. It doesn't follow the 12 grid structure that I could have pulled off. There's only the desktop design and I'm supposed to wing the mobile and tablet as I go. To make things worse, I'm using a page builder on WordPress to do it because the client wants to be able to reuse elements using these blocks on the page builder.

@exceptionalGuy 12 grid sounds like you're still stuck with percent based columns from bootstrap, try something like tailwind css, which makes use of less restrictive flexbox.

@JoshBent sounds like Greek but I'll look it up. Thanks man. :)

@exceptionalGuy https://tailwindcss.com/ also a quick fact: the people behind it have amazing design tips on their own twitter accounts, worth checking out too. (e. g. shoger)