This is my DIY light tent.  It is made of 1/2" PVC tubing and fittings, clips for attaching the sweeps and a plain white bed-sheet.  Mine is quite large but you can make it any size to fit your needs so I haven't included any measurements.  It disassembles for easy storage.

This is the tent assembled (without sweep):

Interior details.  There is a rail that slides along the top frame rails which is useful for hanging items like ornaments.  The clips on the far rail are for attaching the sweeps:

It can be dismantled quickly and easily for storage. It is easiest to remove the front upright supports first. Then the rear uprights should be fairly easy to remove once the front ones have been removed:

You can dismantle it completely or partially depending on what your storage needs are:

Here is what the frame looks like without the cover:

Here is a detail shot of the fittings: 

Sliding rail:

Top rear bar with clips:

The cover was made by pinning a white sheet onto the assembled frame, trimming the excess fabric, removing the cover from the frame and then stitching it together. I can barely sew a button so I am no seamstress but if I managed to do this I am pretty sure almost anyone can. It does take some patience.

Assembly is easy after the first couple of times.  Insert the top and bottom pieces into the cover and align them with the rear corners on the cover:

I fit the front uprights into the top corner fittings and the front corners of the cover before installing the rear uprights.  Do not install the front bottom section of the frame at this point:

I then install the rear uprights. The bottom front corners of the cover do not get installed into the fittings just yet so that it is easier to assemble the rear uprights:

*The front cross piece can also be removed when desired if it gets in the way of some shots.  I've never had an issue with the cross piece getting in the way but mine is quite large.  I use the front cross piece to secure the front of the sweeps to keep them from curling or shifting: If you make a small one the front cross piece may get in the way.

Lastly install the sweep which can be fabric or paper:

The final step is to have fun experimenting.  You can use all sorts of light sources even natural light like this which is through my dining room sliders:

Result:

*If you are using a reflective floor like black glass or a mirror you may need to run the sweep across the top or put black foam core between the frame and the cover.  You can also angle black foam core from the back bottom to the top using the adjustable bar to hold it in place at the desired angle so that the frame is not reflected in the surface of the glass or mirror.

I hope that you have found this useful and will look into making one for yourself.  If this one seems too complicated for your tastes there are lots of other ideas out there.  All you need to do it Google Do It Yourself Light Tents.

*HINT: Use custom pre-set white balance when possible to get the best results.

*HINT: Cut the leftover fabric into panels which can be used to add more diffusion to the top or sides when needed.

Have fun!