Hi,

I'm wondering how you make earthworks for 6mm. Trenches, fortifified walls, gun emplacements, etc. Any advice?

There are some nice trench frames available from commission Figurines http://www.commission-figurines.co.uk/wp-content/uploads/2021/06/Commission-Catalogue-2021.pdf very cheap, you just fill them with air dry clay.

Have a look at  6mmacw.com   which has a building scenery section which includes defences and forts. This stuff can be used in other eras. Click on 6mm terrain tips on the tab.

Depends exactly what you want but quarter rods are pretty good for this kind of thing:

triangular rods with a right angle, or near enough, work well too, depends what you want the front to look like.

cut them as a single piece, or you cut them into three pieces, with angled cuts so you can set back the two flank bits if you want. cut out or file down bits for where the guns fire from. Like this kind of thing:

Have a look at the Kallistra site as they feature some trench and gun emplacement modules. Although nominally scaled for slightly large figures they will probably work quite well.

And Irregular Miniatures have a variety of bits in their 6mm scenic range and the Pendraken site is always worth a look.