Now it's not that hard, It would be much more beneficial if you drew it and asked for corrections.
Take everything to the left of the output of IC1 from the, again, nicely documented, EE article (you don't need C3 as the LM358 is unity gain stable) and patch on everything to the right of the output of IC2/a (including D4) from Not1Xor1's design.
Not that hard for you... maybe! I'm just about to crack open BBox 1 and start learning electronics. I can just about read the diagrams, get the bits and wire it together. I'm not yet at the stage where I can understand to the point where I can create my own circuits. I can throw kits together, but don't ask me how or why they work. If something doesn't work when I've built it, I've got no skills to troubleshoot it.
For years, I've been bodging things together and hoping they don't go bang. How I've made it this far without causing a fire, I don't know. Probably by sticking to 5v DC at a guess So yes, some way down the road I'd be happy to take on the challenge. Right now, however, I'm not up to the task.
Sorry for overestimating your position on the learning curve (or maybe deliberately setting you a bit of a stretch goal
). The 'cut and shut' is literally what I put in my post anyway. It just takes the audio oscillator part the Not1Xor1 design and uses it with the Everyday Electronics one as you have an opamp spare (half an LM358) and you probably don't have a CD40106. At the end of the day, battery consumption is a little bit higher but that doesn't matter.
The reason I pushed the Everyday Electronics one is (as I keep banging on about), it has a good low level description of how it works, how it was designed, and why components were chosen, apart from just being a good one. Back in the golden days, Everyday Electronics was launched as a beginners version of Practical Electronics which launched in the mid '60s. They needed another one for the people who hadn't 'grown up' with PE (which is where many of us oldies got the bug).
Luckily you can read the full set of issues for free. At your knowledge level a lot of fundamental things haven't changed (if you ignore the arrival of the micro, Arduinos etc), and most of the 'old faithfuls (like the LM358) are still available. EE and PE eventually got merged into EPE which still lives today, although a lot of the articles are reprints from the Australian Silicon Chip magazine, which seems in rather better health.
I really would recommend that you dig into the old EE issues, they had lots of bottom of the learning curve projects and teaching series (analogue and digital) which are just as relevant today, and are
far better written than a lot of patchy, superficial web content you get these days....
https://worldradiohistory.com/Everyday_Electronics.htmP.S. You can find PE, earlier EPEs and other mags there too.
EDIT: Just a note that safety standards have changed over the years if you are looking a any of the mains related projects!