So, how do you exactly use archers as chaff? I'm having a hard time with them getting in the way of my own charges of the enemy doesn't charge them, and since they are skirmishers, I can't really redirect the enemy to the side they they just overrun into me if they do charge.
Honest question, I want to play better.
Depending on what unit you need to absorb, and on what unit they are a detachment of, the standard idea is to put them in front (4"-5") of your unit, say a block of spearmen, covering the whole front, in skirmish formation.
This way you have 3 different options when they are charged:
1-stand and shoot. This is in particular useful when they get stubborn from being a detachment of a greatsword unit (or any veteran state troop with the banner that gives stubborn). If they are wiped out it is what it is, but if they survive, they can FBIGO automatically. It's not imho the best usage of a chaff archer unit, since their point is to have the enemy make a failed charge thanks to running away, so that you can charge them back the next turn. It is useful if you need to make the enemy unit waste spacial rules like first charge that only happens appen the first charge (or combat) of the game but keep in mind that this makes you vulnerable to ovverruns (i.e. the enemy unit charging again). If you out your archers very close to their parent unit, like 1", the enemy unit might get a very small I bonus from the overrun. Still they get to use their lances and whatnot, so you need to build this "trap". Earthen rampart from the elementalism lore is a useful spell in this case.
2-Run away. It's pretty straightforward, you don't get to use their bows but you still use archers because they are the cheapest unit around that can skirmish. The flee movement is 2d6, so 7" on average so even outting them 5"-6" in fron of their parent unit should be enough to cause a failed charge, while at the same time the enemy unit will move the whole charging distance (not just the higher d6) because the failed charge was caused from the target fleeing. This is the best usage if you want to the. charge the enemy unit in the next turn, since it will probably be pretty close to yours.
3-Fire and flee if you buy it. It's basically both of the previous options, you get to shoot and flee afterwards. The main issue, when use with infantry, is they they will flee only the highest of 2d6, so let's say aroun 4" in average, and putting your parent unit only 4 inches behind the archers might not be enough to prevent the enemy from redirecting a charge to the unit behind. That said there are a couple of tricks that a skirmishing unit can use here, for example you could put a couple of your archers each 1" towards your unit behind, so that while the fron of the archers is 5 or 6" in front of the parent unit (or simply the unit behind) the rear-most archer models are only 3 or 4 inches. Since units flee directly from the charging unit, the rear-most archers will end up within the unit behind more easily, thus forcing the fleeing skirmishing archers to pass entirely through the unit behind them until they clear it on the other side.
The last one works better with outriders, since they have swiftstride and can use it to flee 2d6 even if they fire and flee (technically they flee 2d6 discard lowest+1d6 from swiftstride).