I have been meaning to make a tut for this since I have the technique pretty well perfected. I never get decent results with multiple "passes" and it seemed like a PITA waste of time. YMMV.
Super sort no pic version.
1. Use a sanitized 1.5L wine bottle and fill it 1/2 full like you would if you were bottling it.
(You can use a smaller one but it is a waste of time IMHO. I actually use x2 1.5L wine bottles because it makes the process faster and if freezer space wad more available I would use more.)
2. Carefully press a cork into it by hand as far as you can. This should leave some cork not in the bottle.
(FYI I like the synthetic cheap corks because they last a long time.)
3. Lay the bottle down in a freezer so the NECK has minimal/no liquid in it.
4. Wait 12-24 hours. If it is slushy wait longer. When you pic up the wine bottle by the neck the ice should be frozen enough to stay in place when vertical and look like it is frozen.
5. Remove cork and pour into a 2L Erlenmeyer Flask or some sort of "jar". Then invert bottle so that it stands on it's own.
(I prefer my 2L flask because when the wine bottle opening gets submerged it just backs up into the wine bottle. The flask will hold the bottle opening out of concentrate for about "4 batches" starting with 17% ABV wine.)
6. Wait. LOTS of color will drain into the bottle. I leave mine for about an hour or until it looks like brilliant white snow and it seems like you have gotten what you want.
7. Carefully remove the bottle and set it aside with the cork in it.
8. What is in the flask is your concentrated beverage.
9. I try to mix wines that I do not care much for into the left overs that were in the bottle and a small amount of Irish whiskey. It is very "dry" and goes well with cheese but is thin and watery so is great for session drinking.
I Just aged 3 gallons of mom's dry applewine on some Jack Daniels whiskey barrel chips for 6 weeks and concentrated it down to just over a gallon. Since I did not remove all the alcohol and sugar in the frozen liquid I estimate that I probably came in just under doubling my ABV to 25%-30%. Then I added about 500ml of Jim Beams "Devil's Cut" (45% ABV) to it. While each step of the way it tasted different, I REALLY like the end product as a "sipping drink" more than I liked any of the individual components that much.
Now, I need to get a glass... I like it "neat".