Washed this cotton blanket now it’s stiff :( how can I soften it before gifting?

I used paintbox dk cotton yarn, when I made the blanket it was so nice and soft. Then I washed it, and laid it out to air dry (the yarn says do not tumble dry) and the cotton felt quite hard and generally pretty gross. I tried soaking it in warm water with conditioner but that hasn’t seemed to do anything