What about squirrels? Can they get into these bags?

Squirrels can get into anything. They're squirrely.

There was no instructions included. Can someone pls explain how to use this potato grow bag pls?

I put about 6 inches of soil in the bottom of bag, then place 2-3 seed potatoes in and then put enough soil in to cover at least 1 inch over the seed potatoes. I then roll down the sides of the bag to let in as much sunlight as possible. Water regularly and add soil as plant grows, leaving an inch or so of leaves showing. As the plant grows roll up sides of bag, add soil, and water. When bag is rolled all the way up let plant grow continuously, pruning flower buds to promote tuber growth. Hope this helps.

How would you recommend planting potatoes? Place 3-5 slivers in the bottom, cover with soil, wait to see sprouts, cover with soil and repeat?

Add about 3 inches of soil mix with organic matter, like chopped leaves , then plant about 5 WHOLE potatoes. I do not cut them at all. Cover with 4 inches more soil and organic matter and fertilize with organic vegetable fertilizer. Leave the bag where it gets morning sun and shaded from hot western sun. I always roll the top of the bags down so the plants are not left in a dark hole and unroll it as plants mature. Each time the plants grow 4 or 5 inches add more soil, leaving 2 inches of plants showing. Do not use manure. When the plants are over the top and your bag is unrolled all the way add another sprinkle of vegetable fertilizer scratching it into the soil and mulch with straw or chopped leaves. Do not overwater. When the plants bloom then you can check the bottom of the bag through the plastic flap for new potatoes. Harvest after plants are dying and turning brown. Check the Farmers Almanac and do not harvest on a water sign. If you do they will rot. Heirloom Seed Supply.