I have been using this for 5 seasons now for chipmunks but I have had quite a few of the small to medium size squirrels fall prey to its seedy allure

Simple 5 gallon green bucket from May-nerd's (yes I know it Menard's). Tried an orange Home Depot bucket and they wouldn't come near it for some reason.
Scrap 1x6 approx. 30" long
Krappy azz peanut butter form the $ store.
20lb bag of sunflower seeds (also from May-nerd's)

Place in a varmint high traffic area. Not under an open window the little suckers scream and scratch at the bucket a little while drowning
1/3 full with water and add seeds to coat the water about 1/2 thick (seeds will float for about 2 days)
4 small dollops of PB on the ramp with a sunflower seed on top of each dollop.
Check daily with a large slotted spoon (use the old one in the kitchen, it is now the dead varmint scooper)
Drain and refill as needed.

I started to track the kills with a sharpie on the bucket in 2018.

2020 tally
Chipmunks: 9
Small to Med Squirrels: 9

2019 tally
Chipmunks: 21
Small to Med Squirrels: 7

2018 tally
Chipmunks: 24
Small to Med Squirrels: 12