Edit: I just realized there are a whole bunch of videos from people who have completed the challenge that I can go watch to find my answers instead of posting here. LOL So nevermind.
Well thanks to your tip, I was indeed able to make a Mesh, and thus, make the Mesh Sieve, but I don't know how to "turn it in" so I get credit for the first Achievement. Doesn't this Skyfactory Challenge thing come with any instructions? LOL I guess it's a map for "experts only".
And I hear ya about Skyblock modpacks, they're not really my cup of tea either. I prefer to have a nice landscape to view while going about my business. Just my own personal preference, most of my friends LOVE the skyblock stuff. To each their own.
But I like the concept of speedrun, because it's a way to practice getting out of my worst habit, which is to be a packrat. LOL Speedrun means you have to learn how to be optimal with your time, and learn how to not hoard items - only get exactly what you need, and no more than that. That's good practice for any modpack, at least for me, because I tend to get bogged down when I play, my progress slows to a crawl, and I lose interest at that point (because I never seem to get anywhere LOL).