Visual Studio doesn't allow you to just make a solution. You are forced to make a project as well. This doesn't lend to flexibility in folder structure.

I like to start with a blank solution file. There's supposed to be a blank line at the top, but this blog's formatting prevents it from being shown:

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio 15
VisualStudioVersion = 15.0.26430.13
MinimumVisualStudioVersion = 10.0.40219.1
	GlobalSection(SolutionConfigurationPlatforms) = preSolution
		Debug|Any CPU = Debug|Any CPU
		Release|Any CPU = Release|Any CPU
	GlobalSection(ProjectConfigurationPlatforms) = postSolution
	GlobalSection(SolutionProperties) = preSolution
		HideSolutionNode = FALSE
	GlobalSection(NestedProjects) = preSolution

Just plop that into a new file, slap .sln on the end of whatever you decide to name it, open it in Visual Studio, and you'll have a blank solution from which you can start clean.