Hi,
Use Ventura "Custom CSS" option in Appearance and and put there something like:
.block.block_totara_featured_links {
border-radius: 5px;
margin-left: 15px;
}
For specific block:
#inst192.block.block_totara_featured_links {
/* Iinstance ID need to fit your block */
…
}
Or you can target css to page type (dashboard) and region (left) etc to make it more general 🙂