As our table is the weird mishmash of 5e '14 and 5e '24 (thanks WoC!) we have always played flanking on our square grid maps. Flanking being generally defined as on opposite sides of an enemy which would force that enemy to have to turn its back to one of the Adventurers thus giving both Adventurers advantage on attacks.
From DMG '14:
If you regularly use miniatures, flanking gives combatants a simple way to gain advantage on attack rolls against a common enemy.
A creature can’t flank an enemy it can’t see. A creature also can’t flank while it is incapacitated. A Large or larger creature is flanking as long as at least one square or hex of its space qualifies for flanking.
When a creature and at least one of its allies are adjacent to an enemy and on opposite sides of the enemy’s space, they flank that enemy, and each of them has advantage on attack rolls against that enemy.”
Research this morning notes that some consider flanking in '14 as an optional rule, though I do not know that any table I have played at did not use it. Sources noted that flanking was a hold over from previous versions and that ADV on the attack roll as implemented in 5e '14 is more powerful than flanking was in previous editions. Some sources noted that with flanking battles tended to form “congo lines” that are silly as natural melees would never end up this way. We had our own mini congo line last night which clearly demonstrates their point. Playing the monk in that congo line, I can note that in my experience getting ADV on 5 swings a turn at lvl 10 becomes crit fishing and is very powerful.
We were quite surprised to learn last night what the DMG '24 & PHB '24 say about flanking: NOTHING.
So RAW in '24 means no flanking.
So as I prep to run a table (which theoretically will be '24) this leaves me contemplating flanking. If ADV is too powerful for flank. As a table rule, what would an appropriate bonus be for attack from flank with out incintivizing it too much? My gut says add a D4 to the attack roll, maybe a D6?
If my monk needs a 10 on the d20 to hit something with AC of 16,
Flat roll swing, his chances of hitting are 50% and almost 5% to crit on any given swing.
ADV on the attack from flank, chance to hit goes to 70% and 10% chance to crit.
Straight attack role +1d4, chance to hit becomes 55-70%; chance to crit becomes 10%-20%. So IMO I guess the D4 nerfs the to-hit but makes the crit chance increase on the average.
Interesting average damage per attack calcs as well, for 1d8+6
Flat Roll: 6 DMG
ADV Roll: 8 DMG
Flat+1d4: 6.75-9 DMG (7.87 Average)
From the probability numbers we’ve seen and calculated, 5e’s Advantage is roughly equivalent to a +3 ability boost. I’m not going into the maths on that here, Alphastream has the rundown if you want it.
That’s a big boost at any level of play, so it’s foolish to ignore if it’s an available option.
What’s been worse for me than the “conga line” of flankings is the way that it conjests the battlefield and interferes with AoE spellcasting - which can do a lot more damage than a martial-melee landing one or two more hits will.
TBH, I’ve never been much a fan of flanking and only included it because players were accustomed to it. I think it would be better implemented as some sort of character option like a Feat or a Fighting Style.
Advantage is also problematic because it doesn’t stack with the bazillion other sources of advantage in the game (even more in 2024). Almost no 5E tables I’ve ever run or played at have bothered with flanking, and I think it’s because the edition doesn’t want to emphasize positioning as much as 3.X or 4E. But a lot of people coming over from those editions (who don’t open the DMG very often) didn’t realize it was an optional rule.
Anyway, if choosing square A vs. square B to stand in is fun, I would just go with a +2, or +1 for each of your allies standing next to the target.