PM> Install-Package Serilog.Extras.AppSettings
... = new LoggerConfiguration()
.ReadAppSettings()
... // Other config
In x.config, add two (or more) app settings keys:
<appSettings>
<add key="serilog:using" value="Seq.Client.Serilog" />
<add key="serilog:write-to:Seq.serverUrl" value="http://my-seq:5341" />
</appSettings>