you not craft attack speed, you theoriecraft it!
if, shield charge does:
0.5sec attack animation, witch happens at the end of the charge animation, witch can be canceled completly with the animation-cancel-walk
1sec charge animation, to travel max charge distance, at +120%increased charge movement speed and boots
you traveled
1sec*2.2speed
and 0.5sec*1.2speed
a avg of 186,6%speed
clicking the flask, +80%movement speed, makes speed be 300% instead of 220%, witch makes the 1sec become 0.7seconds (1/3*2.2)
0.7sec*3speed
and 0.5sec*2speed
a avg of 258.33%speed
increasing attack speed, will allow to start another shield-charge sooner, after you canceled the attack animation
you take 100%increased attack speed, instead of the flask
1sec charging*2.2speed
0.25sec of canceled attack*1.2speed
a avg of 200%speed
if take 100%attack speed and spam flask for +80%movespeed
0.7sec chargetime*3speed
0.25sec of attack time*2speed
a avg of 273.68%speed
273.68/258.33===> 5.9%more shield charge distance traveled from 100%more attack speed