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I think I'm going to make a stout. I was thinking classic dry type, and then thought about the Terrapin Wake and Bake. I think I'll give that recipe a try, but I'd like to try boiling some of the dark malts in the kettle (as flour). Anybody ever try this, or know much about it? I've heard of the technique, but no details. Anyway, here's the base recipe:

28 lbs 2.1 oz Pale Malt (2 Row) US (2.0 SRM) Grain 1 68.5 %
3 lbs 5.6 oz Caramel/Crystal Malt - 80L (80.0 SRM) Grain 2 8.2 %
2 lbs 15.0 oz Barley, Flaked (1.7 SRM) Grain 3 7.2 %
2 lbs 15.0 oz Oats, Flaked (1.0 SRM) Grain 4 7.2 %
1 lbs 3.9 oz Black (Patent) Malt (500.0 SRM) Grain 5 3.0 %
1 lbs 3.9 oz Chocolate Malt (350.0 SRM) Grain 6 3.0 %
1 lbs 3.9 oz Roasted Barley (300.0 SRM) Grain 7 3.0 %
3.00 oz Warrior [10.00 %] - Boil 90.0 min Hop 8 37.8 IBUs
1.50 oz Bramling Cross [6.00 %] - Boil 30.0 min Hop 9 8.1 IBUs
1.0 pkg American Ale II (Wyeast Labs #1272) [124.21 ml] Yeast 10 -

Est Original Gravity: 1.088
Estimated Alcohol by Vol: 9.3 %
Bitterness: 45.9 IBUs
Est Color: 46.3 SRM

Why not crush and do it in a bag as if it was partial mash? I don't think I'd want flour in my hopstopper.

All I could find about it in a quick scan of Daniels Designing great beers:
While talking about stout mashing temps for NHC award winners he said this

Finally, three recipes called for boiling of dark grains for ten to thirty minutes. I have not encountered this practice previously and would be reluctant to try it myself, but obviously it has worked for some brewers.

Not much help, sorry.

Good luck.

That's probably where I read about it. Not too worried about the malt in the kettle, my hopstopper design will handle it.

An old 'trick' at breweries brewing dry Irish stouts is to hold back about 10% of the roasted barley from the mash and add it to the boil for the duration. I do it all the time when brewing black beers.

Many breweries grind the black roasted malts into powder but it's not for flavour change, it's to maximize extraction efficiency. You can likely cut back the overall quantity required for colour and flavour by 10 - 15% with the same results.