Change Slick Grid column width

           
You can use minwidth property to change column width
   var checkboxSelector = new Slick.CheckboxSelectColumn({
                  cssClass: "slick-cell-checkboxsel"
                    });
                columns.push(checkboxSelector.getColumnDefinition());
                  columns.push(
    {id: "sample_id", name: "Sample Id", field: "sampleid", minWidth:120},
    {id: "customer", name: "Customer", field: "customer",minWidth:200},
    {id: "type", name: "Type", field: "type",minWidth:120},
    {id: "priority", name: "Priority", field: "priority",minWidth:120},
    {id: "standard", name: "Standard", field: "standard",minWidth:120}
    // {id: "test_group", name: "Test Group", field: "test_group",minWidth:120}
                   );

 for more option see:  https://github.com/mleibman/SlickGrid/wiki/Column-Options