It depends on your resources and time frame. You could order a ferrel like this and weld it on the lid.
https://www.brewershardware.com/...Clover-Ferrule-Long.html
Then one like this for pipe side solders on.
https://www.brewershardware.com/...lover-Ferrule-Short.html
and of course the tri-clamp to go with it.
https://www.brewershardware.com/1.5-Tri-Clover-Clamp.html
Thats about 15 bucks and you have a very secure sealable connection. If you don't have the means to weld the ferrel onto the lid you could probably get it done at an exhaust shop though youd have to play that one by feel.
Otherwise you can drill and tap the lid, depend on how thick it is and your access to a fairly expensive 1" tap.
If you have mapp gas or an oxy actelyne torch you drill or dremel a hole to fit your npt fitting and then braze it in with food grade silver braze. Once done it makes a sturdy joint. Its expensive as all heck though. I paid 50 bucks for 6 sticks.
Again depends on what you got to work with and your time frame. I think the tri clover clamp is the best route to go personally.

I have a bunch of ferrels here and see no possible way to bolt them down. The flanged end goes up.
If you live in or near a city i would just take it to an exhaust shop that does stainless. They will likley do it very cheap. Its nothing to them, take longer to set up then to weld it. Or put out feelers amongst friends for someone with a mig or tig welder. Just tell them you are making beer and its a fitting for a temp probe for your mashtun.

Why be an ass? Its a homestill, not a ghetto still. Take a look at some commercial stills then look at what you got. Its all ghetto compared to the real thing.
Look at that huge tower in the background. Wicked.
Carl stills

This is what I was trying to describe. I meant flange when I said ferrule. Sorry, I usually come off as stupid.

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Its all good. I can't recall if i've seen anything like that at the hardware store or not.

Here it is from acklands.

http://www.grainger.com/Grainge...-Flange-1WLH5?Pid=search"

teflon tape or edpm o-ring or flour paste. Im not sure but i wonder about a regular old cork gasket? Easy enough to make if you have some gasket stock. No silicone. You can use silicone to seal the tubing and fittings in your condenser as that does not touch product.

Some more copper porn for the fun of it.

Does the size of the boiler matter? I have an electric stove, and would like to use it, but I don't want to wait for ever to warm up. What's the right size? (Keep in mind I have an 18 inch column and 20 foot x 1/2 inch condenser)

The big element on a stove is 240v and 2500watts. Substantially more powerful the a 120v hotplate. The problem is its easy to crush the burner by overloading it. If you use some nuts or washer to support the weight of the pot you can really load it up. The burner will easily produce at 1 gallon and hour plus. You won't be able to run that fast if you want decent flavor but the burner is plenty capable.

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Your stove doesn't cycle. You ever used one? Cmon on dude. Those crappy heating hotplates cycle, not a stovetop. Put your stove burner on high and see what happens. It turns red and stays red. A hotplate not so much.
Who would you listen to, the person that's done it or the persons that's heard about?"

Well hmm..the high dollar yup cook stove like I got cycles like a mofo. Yall must have a cheap off branded non cycling model..lol.