Stereo is by definition 2 channels,, left and right, each coming out of a single speaker.  This is why you can't combine 4 speakers and have it be "stereo".

Can I use an amp with one and one sl as a stereo setup?

You don’t need a Sonos Amp to set up the One and One SL as a stereo pair. They are paired without the Amp.

Read more here:

https://support.sonos.com/s/article/1066?language=en_US
 

The Amp is designed to power a set of passive speakers.

If you want to play the Amp/passive speakers together with the One/One SL pair, you can group them together in the Sonos app.

I am using tv arc to amp and want just stereo system with one and one sl 

This isn’t possible. You could group the stereo pair of Ones with the Amp while playing TV audio, but you will probably experience a slight audio delay.

Your only option is to get a pair of passive speakers to connect to the Amp. The One and One SL is not designed to be used as standalone TV speakers. If you don’t want to get passive speakers, you might consider getting a Sonos sound bar like an Arc or Beam to use with your TV.