I want to be able to center a 2x2 plate in the middle of a 3x3 plate - specifically to put minifig on. Another option would be to center a 2x1 plate on a 3x1 plate.
I saw this technique in LEGO's Disney Castle for offsetting parts of a column by half of a stud. You can see the column on the left in this picture is shifting half a stud above a 3x3 plate:
Of course you can do it too! Here is the process:
Take your 3x3 base plate and stick 1x1 "dots" between each of the studs. The "dots" are LEGO part 4073 which BrickLink calls "Plate, Round 1 x 1 Straight Side". So you end up with 4 dots on your 3x3 base. I didn't have a 3x3 handy so I start with a 4x4 to demonstrate:
- Those dots form a new layer that is half of a stud off from the base plate (3x3 for the OP, 4x4 in the pictures). So you can just stick your next plate on it. (2x2 for the OP, 2x3 in the pictures)
A friend wanted to verify this and so we get to see the parts originally requested:
If stability is not an issue, consider the following:
Put a 4×4 dish on your 3×3 plate (yes, this fits):
Put your 2×2 plate in the middle (in any orientation you like):
If you want to centre your minifigure, add a layer of 2×1 plates with centre studs:
… and place your minifigure on top:
(This also works with a 1×1 plate instead of the dish, but it looks rather puny.)
Another soloution if rotational stability is not too much of a concern and you don't like having studs on show.
Put a 1x1 plate in the middle of the 3x3 plate and surround it with 1x1 or 1x2 flat tiles so you have a 3x3 surface with a single stud popping up in the middle.
You can now stack a 2x2 plate on top held in place by the single stud.
In 2017, LEGO introduced a new 1x3 Jumper plate (34103).
The first sets to include this piece are:
As of 2017 the piece is available in black, light bley, blue, medium blue and pink.
Hopefully in the future we can expect to see it in more sets with varying colours.