Hi Michael. Simple questions on surface but actually quite complex underneath.

Leaf mold - Firstly, this not the same as compost. It is great for digging into your soil as a conditioner but contains very little nutrition. Compost on the other hand is rich in nutrients. Don't let that put you off though, it is well worth making some and using it as a soil improver. You should make some holes in the plastic bags and then put plenty of water in. You may think it is crazy to make holes for the water to escape but the whole point is that it wants to be damp, not swimming. Leave it for at least 6 months in a shady outside place (I leave mine for a year) making sure it does not dry out. And that is it. Dig it in or use it as a mulch as necessary.

Seeds - most will keep for a while, some up to 3 years if kept dry and cool but parsnips are not one of them. Foil won't help much, parsnip seeds have a very short shelf life so have to be fresh every year. If you want long life then grow corn. I've had it germinate after 5 years.

Hope this helps.

I rake up leaves and put them in black dustbin bags, then pour a bucket of water over them, then punch some holes in the bottom and fold the tops over and make sure they don't dry out, I put mine behind my summerhouse for a year, you can also run a lawnmower over them first to chop them into smaller pieces then they compost quicker, if you have a drive way you could chop them on there, your neighbours will think you are going mad though LOL.
Jackie :o)))

I also make leaf mould the same way but as mine are beech they take 2-3 years to break down. I also add a sprinkling of soil to help 'seed' the leaves with the various microbes needed to break the leaves down.
The bags go out of sight behind the garage.

I make lots every year and I find mine takes around 9 months. I mow them up or use my leaf hoover to chop them up, also find the secret is to get a variety of leaves and not to have them too wet.
Once in string bags or plastic bags full of holes I stack them in my shady wooded area and hope for very cold weather as unlike compost which needs heat leaf mould needs cold conditions.
In my area which is wooded I dont gather them just leave them on the ground to do their own thing.