From a 98 Forester? it can't stay in the house forever...

I keep a spare gas can around so I can put low quality gasoline in it. Then in the winter I mix this gas with used motor oil to light the wood stove in my shop. I pour all of the gas out of the filter that I can get out of it. Twist and turn it around over a funnel until no more will come out. Then I put it in a plastic bag and throw it away. I use contractor grade garbage bags in my shop to try and keep leaking to a minimum.

as mentioned.....dump out all the gas you can, and throw it out. If you want to let it sit for a little bit for more of the gas to evaporate, that's fine.