In $R^7$ there are distinguished 4-dimensional area-minimizing submanifolds called coassociative 4-folds, which have proved relevant for studying regularity theory for minimal graphs in higher codimensions, as well as in $G_2$ geometry and theoretical physics. Locally coassociative 4-folds are abundant, and one can find many examples through complex geometry, but otherwise global examples are rather scarce. I will describe gluing constructions for coassociative 4-folds, which in particular yield infinitely many new embedded coassociative 4-folds in $R^7$ which are asymptotic to cones at infinity. This is based in part on joint work with Nicos Kapouleas.