You dont need a mold, but you do need to lay a flat even bed of thin set to flip your mosaic onto. A tabletop is perfect for this. Maybe this will help.

Here is a link that might be useful: Indirect method

Just read the instructions in the link and they are quite helpful. It sounds more difficult to explain than it is to do. You are mosacing upside down. Once the water-soluble glue that holds the brown paper to the mosaic surface is dry, it is fairly easy to flip the entire mosaic over. Once it is flipped over and glued down to its substrate and That glue is perfectly dry, it is easy to soak the brown paper off and peel it away. Voila! A flat mosaic. More complicated than the direct method, but so nicely flat. Doing a small piece first to get the gist of it will help.

Laying the adhesive bed is probly the hardest part, Ive seen some good directions somewhere....but you use a notched trowel to lay the adhesive to an even thickness.

So Silvamae: You let the thinset dry completely before you wet the paper to peel it off your tiles? Maybe that's what I'm doing wrong. I've been trying to wet and peel the paper off while the thinset is still soft, per instructions I have in a book.

One thing I learned (the hard way) is to not use too much glue to stick the tiles to the paper. All the water in the world won't get it off without pulling the tiles off the thinset.

I'm thinking of giving the mesh thing a try instead, but I'm often working with very very small tile pieces (1/4" squares). Wonder how mesh would hold them on.

Wait. You use a water-soluble glue to glue the tile face-down to the brown Kraft paper. Such as Weldbond. Not thinset. If I'm understanding you correctly. Come back on here and let's discuss. If you were to use thinset to glue your tiles down to the Kraft paper, you would not be able to get it off. There are two separate steps here and two different types of glue. (Sorry if it takes me awhile to answer; one) I am away a lot this week for doctor appointments, and two) my granddaughters take over the computer for hours at a time.) But I will check back.

No, Elmers glue mixed 50/50 with water to glue the tops of the tiles to the paper. Thinset to glue the bottom of the tiles to my concrete base (I'm doing outdoor mosaics).

I thought I was saving time by dipping the tiles in the Elmers using tweezers instead of brushing it on with a paint brush. That left way too much glue on the tiles and I had a really hard time getting the paper to peel off no matter how long I soaked it. But I also did not let the thinset harden before trying to pull the paper off. In a book I have, the author soaks the paper off while the thinset is still soft, that way you can adjust any tiles that don't look right.

I grew up doing mosaics using the direct method, so I'm still trying to figure out the indirect method. I like that it allows me to follow a pattern, but it's tricky. I've been wondering if mesh would be easier. I'd get the benefit of having a pattern underneath the mesh, but not the hassle of having to create the piece upside-down or pull paper off once the tiles are glued.

The only way I have used the indirect method is in a stepping stone mold. First coat the mold with Vaseline or mold release. Then the paper pattern (reversed), cut to fit exactly, is laid down. Then contact paper, sticky side up, again, cut to fit exactly. Then mosaic, pressing the front of the tiles firmly to the sticky surface. Then pour Diamondcrete to fill the mold. Then tump out and voila, a perfectly flat stepping stone.

Yes, if I'm going to do the indirect method, I've had way more success with sticky paper at the bottom of a concrete mold. Though that limits you to things you can pour into a mold. Lots of my concrete is hand formed over armature so I've got to either use the direct method to mosaic it, or indirect using brown paper.

I'm still trying to figure out how to get the brown paper method to work consistently. Not sure it's worth all the trouble. If I want to work off a pattern, it might just be easier to trace the pattern onto the concrete and use the direct method.

All the tuturials I've seen use a bunch of small pieces. Does this work for example with those ~1 square inch tiles? What about a combo of 1 square inch tiles and half marbles?

I have not had good results using the indirect method with half marbles. For sure, you need to stick the flat side to your paper, so that will be the side that shows in the end, not the rounded side. And thanks to the texture of that flat side, I never get a nice clean circle from them. I've done it, mind you. But they come out significantly nicer if you use the direct method and have the rounded side exposed.