Is it possible to do slow cook things using a sous vide machine?

Sous vide cooking is often at low temperatures, for long periods of time. But, you lose out on things like evaporation which can be essential for slow cooked meals or certain types of flavor development. You can't do things like stir food in a sous vide setup easily. So you have to be careful with what recipes you convert to sous vide; some will be easier and better if you don't use sous vide.

People do use mason jars for sous vide cooking, e.g. to make cheesecakes/custards. But most things are done in plastic bags (ziploc freezer or vacuum bags).

If you'd like a setup that can sous vide and slow cook and you have an oven, you could buy a dutch oven and a sous vide circulator to put in it (e.g. something like Joule since it sticks to the bottom of the dish magnetically). For slow cooking, put the stuff in the dutch oven, leave the dutch oven covered but open by a crack and stick it in a low oven (225 F ish). For sous vide, put water in the dutch oven, put the circulator in and go. As The Food Lab states in their pressure cookers > slow cookers article, the dutch oven setup described prior will often give you better flavor development and is not necessarily any worse than slow cookers on the safety front. You also have versatility, e.g. you can increase the temperature to 300 F make a slow cooked tomato sauce and take advantage of the maillard reaction better and things like that.

Alternatively, just buy a slow cooker if you really want a slow cooker -- they're super cheap, particularly if you look at yard sales (likely under 10 dollars). The price will be basically negligible next to your sous vide circulator. Then buy whatever circulator you want and use it in an appropriate container.

My first sous vide set up may be exactly what you're looking for. Get a mechanical (stupid) slow cooker (7 quart), i.e. WITHOUT any electronic control. Plug that into a precise PID temperature controller (mine was bought from Auber Instruments in US).

You can leave this setup permanently, as it will have much better control of the temperature than the usual (high) range in which slow cookers operate.

The PID controller has a probe which you'll put into the slow cooker which measures current temperature. When that temperature is one degree off from the target temperature, the controller will switch on (or off) which will turn on (or off) the slow cooker heater.

Depending upon what you're doing, the slow cooker pot will be filled with water or food. I use both methods of cooking regularly.

I am going to be the dissenting opinion here, kind of. I have had decent luck using my sous vide cooker as a slow cooker. You can put soups, stews etc in bags or Mason jars and submerge them in the sous vide water bath to achieve similar results. As someone else stated you can't get any browning or evaporation this way but for a lot of meals that you would do in a slow cooker this works.