I do not know where GiGi's video was filmed but you will not find crushed sea-shells in 98.6 percent of the U.S.
Do NOT put down fabric, it is a waste of time, from years experience.
IF, if you are in an 8a area where it can freeze in winter , plus you are in a muddy area, you MUST dig a deep base or your paver with tilt kitty-whompuss, or sink, in a short period of time.
I do not know how you will space them or if you want something growing between them , plus possible future traffic, but you should dig down at least six inches, eight would be better, tamp that area down well, fill with preferably crushed granite (though use what is available in your area) compact it wel till the addition of sand and thickness of pavers will bring it to level you want. Screed it level or figure in any slope you want (slope makes water run off, not pool) put down one-half to one inch of dry sand and lay your pavers.
You could use a 4x4 , long enough to reach from end to end, to tamp them so they all sit square with one another, including what ever slant you may wish.
If you space them as in the picture it will be a lot more difficult job, to do in a manner that in a year or two they do not get kitty-whompuss, than if they were sitting next to each other with a x fraction of an inch spacing.
Because this a muddy area, it is more important to get the base done right, that in a dry area.
Photo of surrounding area would be a help.
You MUST dig out an area at lease one foot wider on all sides to have room to work. (A motorized compacter is a hundred time better than doing it by hand.)
I would not bother with the round one but that is up to you.
