The mash schedule is complicated, and it will begin EXTREMEMLY THICK. This is necessary because you will end with a lot of water, even at this thick of an intial mash.

Turbid mashing requires removal of the watery portion of the mash, you will be doing a lot of transferring and near-constant temperature monitoring. The volumes of water in the mash schedule are rough guidelines, Focus on hitting the target temperatures. This is the mash schedule from Cantillion in Brussles,
It can also be found here (https://www.morebeer.com/articles/Brewing_Lambic_at_Home ) if you need more information. You WILL NOT achieve a positive iodine-conversion test.

This may seem like a lot of work. IT IS. But it is necessary to achieve the right profile for the loooonnnngggg fermentation and food for the bacteria.

On that note, I was fortunate enough to live within an hour's drive of Lembeek, Belgium, and was able to do an overnight coolship inoculation at the home of Lambic, and "acquired" a sample of yeast and bacteria from inside a lambic brewery The yeast mix in the recipe is as close as you're going to get outside of Flanders.

THE HOPS. This is very important; you need to buy them AT LEAST 6 months before you plan on brewing this. 4oz of hops, opened, poured out onto a tray, and left in a cool, dark, open-air setting to age. They will lose all color and turn yellow, all hop aroma will be gone, as well as the bitterness. They will begin to smell 'cheesy' when they're aged enough for use. DO NOT USE FRESH HOPS.

Fermentation. Settle in, this is going to be a long one. Primary fermentation was 6 months. The beer should develop a thick white bubbly pellicle, and you will notice ropey sections hanging down into the beer. Let your airlock go dry for a few days to a week before refilling throughout the fermentation. The microbes will need the oxygen. At the end of the 6 months. the beer was divided into two carboys to make room for the addition of 8lbs of sour cherries. Don't bother washing them. Either freeze and thaw or lightly crush before adding. This will kick off a secondary fermentation, not as vigorous as the first, but enough to say again: split this between two carboys after primary. Wait another ~6 months, the cherries will sink and begin to break down. rack off the cherries into a third carboy and let it settle for about a month.

Bottle condition this beer, and age it. Aim low with the priming sugar. It will reach the desired high level of carbonation, as bacteria continue to ferment in the bottle. This beer didn't get really good until a year in the bottle. I first brewed this in 2014. I write this now in 2021 - 8 years in bottle, and it has only gotten better. This is worth the effort, I promise. It is the best lambic I have had outside of Belgium, and better than a lot of lambic IN Belgium (That's the opinion of a Native Belgian friend)

Your patience will be rewarded.