My current favorite extraction method. Let buds dry for a day or two, just until the leaves russell but buds are still plenty moist, then stuff into a 2 liter plastic pop bottle with the bottom cut off and a hole drilled in the cap, tamp it down well with the bottom of a jar or whatever. No filter required, it slows down the solvent too much and can cause it to back up in the bottle/column. Just a hole lets it go through nice and quickly, you can filter it later if you want.
You rig the bottle up so it's over a 1 liter measuring cup, or some other container, with a few inches of clearance between the bottle hole and the bottom of the container, so it doesn't sit in the pool of iso after it comes out. I use some wire and tape myself to brace it upright. Put that whole rig in the freezer at coldest setting, along with a 500 ml bottle of iso, for a couple hours or so. Then you pour the whole 500 mls in the top of the bottle nice and even and put it back in the freezer to drip out for a while, like half an hour, until the drips are very far apart if any.
Now here's a part that I use myself, you can skip it and simply evaporate the iso if you prefer. I don't like the vapors so what I do is pour it into a glass bowl of deionized water with salt and a little citric acid as preservative. I use enough water that it's diluted to less than 50% iso, probably more like 20-30%. The salt helps break the emulsion, which looks white. I put a silicone cover over the bowl, which seems safe with iso, and put it in the fridge for 3 days. The precipitation is that slow, though most drops out after the first day. When it's all dropped out, the water looks a lot clearer, so that's kind of a visual cue as to the status of drop out. Anyway then I put the bowl in the freezer to get it quite cold but not frozen, so the extract will get solid so the water can be poured off easier. You can let the pour-off sit for more time to see if anything more drops out.
When warmed back up, I add pure water and mix it around with a spoon to wash the extract of salt and citric acid, a few washes. BTW if it was sort of powdery after dropping out I heat it in a microwave enough to melt it into one mass before washing it. After the dropping out and washing, it's just a matter of letting the water dry out of it. I just heat the bowl up a little, not to boiling or anything but fairly warm, spread the extract around the bowl so it's in a thin layer, and let it sit out in the air for a couple days. It gradually runs back down to the bottom into a pool so I spread it back out every so often. It dries, kind of like paint, becoming more transparent and less cloudy as it gets drier. I guess terps would dry off, but I'm not all that concerned about it myself. You could do it in a vacuum, I just find air drying doesn't seem to hurt it any and is simple to do.
Once dry, you can collect it on parchment in a blob and it will flatten out into a disk over time at room temperature and after about a day it will set up into an olive color with fudge consistency, which makes it convenient to handle, like hash. You can peel the paper off the disk and it's a solid object that you can snap pieces off of. It will only set up like that when you use the freezer method as described. Normal soaked or percolated iso extraction makes a green oil which will never set up and is crappy to smoke, though usable for edibles. I don't know if it will set up as well when evaporated instead of dropped out, maybe. You also can't decarb the weed before extraction if you want it to set up. The fresher the better, which is why I don't even dry it out more than enough to get the volume down so it can all get stuffed in the bottle. I think the moisture also helps when it freezes to keep the iso on the outside of the material instead of soaking in.
