nugetexample.txt

csproj file:

<Project Sdk="Microsoft.NET.Sdk">
    <PropertyGroup>
        <TargetFrameworks>netcoreapp3.1;netstandard2.0</TargetFrameworks>
        <IncludeBuildOutput>false</IncludeBuildOutput> 
        <DisableImplicitFrameworkReferences>true</DisableImplicitFrameworkReferences>
        <NuspecFile>mycontent.nuspec</NuspecFile>
    </PropertyGroup>
</Project>

Nuget File:

<?xml version="1.0" encoding="utf-8"?>
<package>
    <metadata>
        <id>my id</id>
        <version>0.0.44</version>
        <title>mytitle</title>
        <authors>blah</authors>
        <owners></owners>
        <requireLicenseAcceptance>false</requireLicenseAcceptance>
        <description>Content only files</description>
        <dependencies/>
        <contentFiles>
            <files include="**/*.*" buildAction="Content" copyToOutput="true" flatten="false" />
        </contentFiles>
    </metadata>
    <files>
        <file src="../../../../myfile.txt" target="contentFiles\any\any\someDir\myfile.txt" />
        <file src="../../../../myfile2.txt" target="contentFiles\any\any\someDir\myfile2.txt" />
    </files>
</package>